Web Cryptography Level 2

A web application may wish to extend or replace existing username/password based authentication schemes with authentication methods based on proving that the user has access to some secret keying material. Rather than using transport-layer authentication, such as TLS client certificates, the web application may prefer the richer user experience provided by authenticating within the application itself.

Using the Web Cryptography API, the application could locate suitable client keys, which may have been previously generated via the user agent or pre-provisioned out-of-band by the web application. It could then perform cryptographic operations such as decrypting an authentication challenge followed by signing an authentication response.

This exchange could be further strengthened by binding the authentication to the TLS session over which the client is authenticating, by deriving a key based on properties of the underlying transport.

If a user does not already have a key associated with their account, the web application could direct the user agent to either generate a new key or to re-use an existing key of the user's choice.

A web application may wish to limit the viewership of documents that contain sensitive or personal information, even when these documents have been securely received, such as over TLS.

Using the Web Cryptography API, the application could do so by encrypting the documents with a secret key, and then wrapping that key with the public keys associated with the authorized viewers. When a user agent navigates to such a web application, the application would send the encrypted form of the document. The user agent is then instructed to unwrap the encryption key, using the user's private key, and from there, decrypt and display the document.

A web application may wish to permit users to protect the confidentiality of data and documents stored with remote service providers prior to uploading.

Using the Web Cryptography API, the application may have a user select a private or secret key, optionally derive an encryption key from the selected key, encrypt the document, and then upload the encrypted data to the service provider using existing APIs.

This use case is similar to the Protected Document Exchange use case, with viewership of the document limited to the user themself.

A web application may wish to accept electronic signatures on documents, in lieu of requiring physical signatures.

Using the Web Cryptography API, the application may direct the user to select a key, which may have been pre-provisioned out-of-band, or generated specifically for the web application. Using this key, the application may perform a signing operation over some data, as proof that the user accepts the document.

A web application may wish to cache data locally, while ensuring that this data cannot be modified in an offline attack.

Using the Web Cryptography API, the application may use a public key contained within the application to verify the contents of the data cache. Previously, when data was added to the cache, it would have been signed by the server with the corresponding private key. By validating the signature when restoring data from the cache, the client ensures that the cached data has not been tampered with.

A web application may wish to employ message layer security using schemes such as off-the-record (OTR) messaging, even when these messages have been securely received, such as over TLS.

The Web Cryptography API enables OTR and similar message signing schemes, by allowing key agreement to be performed. The two parties can negotiate shared encryption keys and message authentication code (MAC) keys, to allow encryption and decryption of messages, and to prevent tampering.

A web application may wish to interact with the structures and message formats defined by the IETF JavaScript Object Signing and Encryption (JOSE) Working Group.

Using the Web Cryptography API, the application may read and import keys encoded in the JSON key format (JWK), validate messages that have been integrity protected using digital signatures or MACs (JWS), or decrypt messages that have been encrypted (JWE).

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words MUST, REQUIRED, and SHALL in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

The following conformance classes are defined by this specification:

conforming user agent: A user agent is considered to be a conforming user agent if it satisfies all of the MUST-, REQUIRED- and SHALL-level criteria in this specification that apply to implementations. This specification uses both the terms "conforming user agent" and "user agent" to refer to this product class.

Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)

User agents that use ECMAScript to implement the APIs defined in this specification MUST implement them in a manner consistent with the ECMAScript Bindings defined in the Web IDL specification [WebIDL] as this specification uses that specification and terminology.

Unless otherwise stated, string comparisons are done in a case-sensitive manner. String literals in this specification written in monospace font like "this" do not include the enclosing quotes.

Vendor-specific proprietary extensions to this specification are strongly discouraged. Authors must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in question.

If vendor-specific extensions are needed, the members should be prefixed by vendor-specific strings to prevent clashes with future versions of this specification. Extensions must be defined so that the use of extensions neither contradicts nor causes the non-conformance of functionality defined in the specification.

When vendor-neutral extensions to this specification are needed, either this specification can be updated accordingly, or an extension specification can be written that overrides the requirements in this specification. When someone applying this specification to their activities decides that they will recognize the requirements of such an extension specification, it becomes an applicable specification for the purposes of conformance requirements in this specification. Applicable specifications defined by the W3C Web Cryptography Working Group are listed in the table below.

Specification

Reference

Note

Readers are advised to consult the errata to this specification for updates to the table above.

The specification attempts to focus on the common functionality and features between various platform-specific or standardized cryptographic APIs, and avoid features and functionality that are specific to one or two implementations. As such this API allows key generation, management, and exchange with a level of abstraction that avoids developers needing to care about the implementation of the underlying key storage. The API is focused specifically around CryptoKey objects, as an abstraction for the underlying raw cryptographic keying material. The intent behind this is to allow an API that is generic enough to allow conforming user agents to expose keys that are stored and managed directly by the user agent, that may be stored or managed using isolated storage APIs such as per-user key stores provided by some operating systems, or within key storage devices such as secure elements, while allowing rich web applications to manipulate the keys and without requiring the web application be aware of the nature of the underlying key storage.

Because the underlying cryptographic implementations will vary between conforming user agents, and may be subject to local policy, including but not limited to concerns such as government or industry regulation, security best practices, intellectual property concerns, and constrained operational environments, this specification does not dictate a mandatory set of algorithms that MUST be implemented. Instead, it defines a common set of bindings that can be used in an algorithm-independent manner, a common framework for discovering if a user agent or key handle supports the underlying algorithm, and a set of conformance requirements for the behaviors of individual algorithms, if implemented.

This API, while allowing applications to generate, retrieve, and manipulate keying material, does not specifically address the provisioning of keys in particular types of key storage, such as secure elements or smart cards. This is due to such provisioning operations often being burdened with vendor-specific details that make defining a vendor-agnostic interface an unsuitably unbounded task. Additionally, this API does not deal with or address the discovery of cryptographic modules, as such concepts are dependent upon the underlying user agent and are not concepts that are portable between common operating systems, cryptographic libraries, and implementations.

This specification assumes, but does not require, that conforming user agents do not and will not be directly implementing cryptographic operations within the user agent itself. Historically, many user agents have deferred cryptographic operations, such as those used within TLS, to existing APIs that are available as part of the underlying operating system or to third-party modules that are managed independently of the user agent.

The CryptoKey object represents the bridge between the JavaScript execution environment and these underlying libraries, through the use of the internal slot named [[handle]]. The handle represents an opaque type that is implementation specific, which may not be represented within a JavaScript type, nor is it ever exposed to script authors. In this way, the CryptoKey object is the conceptual equivalent to the JavaScript executing environment as the [[handle]] is to the underlying cryptographic implementation.

These APIs are traditionally built around a notion of cryptographic providers, an abstraction for a specific implementation of a set of algorithms. The operating system or library may come with a default provider, and users are frequently allowed to add additional providers, reconfigure the set of enabled algorithms, or otherwise customize how cryptographic services are provided.

While it is assumed that most user agents will be interacting with a cryptographic provider that is implemented purely in software, it is not required by this specification. As a result, the capabilities of some implementations may be limited by the capabilities of the underlying hardware, and, depending on how the user has configured the underlying cryptographic library, this may be entirely opaque to the User Agent.

This specification does not explicitly provide any new storage mechanisms for CryptoKey objects. Instead, by defining serialization and deserialization steps for CryptoKey objects, any existing or future web storage mechanisms that support storing serializable objects can be used to store CryptoKey objects.

In practice, it is expected that most authors will make use of the Indexed Database API [INDEXEDDB], which allows associative storage of key/value pairs, where the key is some string identifier meaningful to the application, and the value is a CryptoKey object. This allows the storage and retrieval of key material, without ever exposing that key material to the application or the JavaScript environment. Additionally, this allows authors the full flexibility to store any additional metadata with the CryptoKey itself.

By not providing an explicit storage mechanism, this specification assumes that CryptoKey objects are scoped to the current execution environment and any storage mechanisms available to that environment (e.g. Indexed Database API). Application authors rely upon this for the security of their applications; two origins with the same CryptoKey object have full access to the underlying key, and as such, messages from these applications cannot be distinguished, and messages sent to these applications can be fully recovered. Implementors should ensure that no CryptoKey objects are shared between two origins unless the author has explicitly chosen to share (e.g., such as through the use of postMessage)

A number of algorithms specified within this specification perform computationally intensive work, such as the generation of significantly large prime numbers, or through repeated iterations of a particular operation. As such, hostile applications may attempt to misuse this API and attempt to cause significant amount of work to be performed by an implementation, denying access or services to other applications that are executing. Implementations should take steps to mitigate these risks, such as limiting the amount of operations an implementation performs concurrently, requiring user consent for operations that may be known to be disruptive for the executing environment, or defining device-specific limits on attributes such as key sizes or iteration counts.

This specification includes descriptions for a variety of cryptographic operations, some of which have known weaknesses when used inappropriately. Application developers must take care and review appropriate and current cryptographic literature, to understand and mitigate such issues. In general, application developers are strongly discouraged from inventing new cryptographic protocols; as with all applications, users of this specification will be best served through the use of existing protocols, of which this specification provides the necessary building blocks to implement.

In order to use the APIs defined in this specification to provide any meaningful cryptographic assurances, authors must be familiar with existing threats to web applications, as well as the underlying security model employed. Conceptually, issues such as script injection are the equivalent to remote code execution in other operating environments, and allowing hostile script to be injected may allow for the exfiltration of keys or data. Script injection may come from other applications, for which the judicious use of Content Security Policy may mitigate, or it may come from hostile network intermediaries, for which the use of Transport Layer Security may mitigate.

This specification does not define any specific mechanisms for the storage of cryptographic keys. By default, unless specific effort is taken by the author to persist keys, such as through the use of the Indexed Database API, keys created with this API will only be valid for the duration of the current page (e.g. until a navigation event). Authors that wish to use the same key across different pages or multiple browsing sessions must employ existing web storage technologies. Authors should be aware of the security assumptions of these technologies, such as the same-origin security model; that is, any application that shares the same scheme, host, and port have access to the same storage partition, even if other information, such as the path, may differ. Authors may explicitly choose to relax this security through the use of inter-origin sharing, such as postMessage.

Authors should be aware that this specification places no normative requirements on implementations as to how the underlying cryptographic key material is stored. The only requirement is that key material is not exposed to script, except through the use of the exportKey and wrapKey operations. In particular, it does not guarantee that the underlying cryptographic key material will not be persisted to disk, possibly unencrypted, nor that it will be inaccessible to users or other applications running with the same privileges as the User Agent. Any application or user that has access to the device storage may be able to recover the key material, even through scripts may be prohibited.

This specification places no normative requirements on how implementations handle key material once all references to it go away. That is, conforming user agents are not required to zeroize key material, and it may still be accessible on device storage or device memory, even after all references to the CryptoKey have gone away.

Applications may share a CryptoKey object across security boundaries, such as origins, through the use of the structured clone algorithm and APIs such as postMessage. While access to the underlying cryptographic key material may be restricted, based upon the extractable attribute, once a key is shared with a destination origin, the source origin can not later restrict or revoke access to the key. As such, authors must be careful to ensure they trust the destination origin to take the same mitigations against hostile script that the source origin employs. Further, in the event of script injection on the source origin, attackers may post the key to an origin under attacker control. Any time that the user agent visits the attacker's origin, the user agent may be directed to perform cryptographic operations using that key, such as the decryption of existing messages or the creation of new, fraudulent messages.

Authors should be aware that users may, at any time, choose to clear the storage associated with an origin, potentially destroying keys. Applications that are meant to provide long-term storage, such as on the server, should consider techniques such as key escrow to prevent such data from being inaccessible. Authors should not presume that keys will be available indefinitely.

Users of applications that employ the APIs defined in this specification should be aware that these applications will have full access to all messages exchanged, regardless of the cryptography employed. That is, for messages that are encrypted, applications that use these APIs will have full access to the decrypted message as well.

This specification relies on underlying specifications.

DOM: A conforming user agent MUST support at least the subset of the functionality defined in DOM that this specification relies upon; in particular, it MUST support Promises and DOMException. [DOM]
HTML: A conforming user agent MUST support at least the subset of the functionality defined in HTML that this specification relies upon; in particular, it MUST support the ArrayBufferView typedef and serializable objects. [HTML]
Web IDL: A conforming user agent MUST be a conforming implementation of the IDL fragments in this specification, as described in the Web IDL specification. [WebIDL]

The terms ArrayBuffer, ArrayBufferView, and serializable objects, are defined by the HTML specification [HTML].

The terms DOMString and BufferSource are defined in [WEBIDL].

The term byte sequence is defined in [Infra].

The length in bits of a byte sequence is its length multiplied by 8.

A byte sequence containing a bit sequence b is the byte sequence obtained by first appending zero or more bits of value zero to b such that the length of the resulting bit sequence is minimal and an integer multiple of 8 and then considering each consecutive sequence of 8 bits in that string as a byte.

When this specification says to convert a non-negative integer i to a byte sequence of length n, where n * 8 is greater than the logarithm to base 2 of i, the user agent must first calculate the binary representation of i, most significant bit first, prefix this with sufficient zero bits to form a bit sequence of length n * 8, and then return the byte sequence formed by considering each consecutive sequence of 8 bits in that bit sequence as a byte.

Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.

Comparing two strings in a ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the codepoints in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding codepoints in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are also considered to match.

When this specification says to terminate the algorithm, the user agent must terminate the algorithm after finishing the step it is on. The algorithm referred to is the set of specification-defined processing steps, rather than the underlying cryptographic algorithm that may be in the midst of processing.

When this specification says to parse an ASN.1 structure, the user agent must perform the following steps:

Let data be a sequence of bytes to be parsed.
Let structure be the ASN.1 structure to be parsed.
Let exactData be an optional boolean value. If it is not supplied, let it be initialized to true.
Parse data according to the Distinguished Encoding Rules of [X690], using structure as the ASN.1 structure to be decoded.
If exactData was specified, and all of the bytes of data were not consumed during the parsing phase, then throw a DataError.
Return the parsed ASN.1 structure.

When this specification says to parse a subjectPublicKeyInfo, the user agent must parse an ASN.1 structure, with data set to the sequence of bytes to be parsed, structure as the ASN.1 structure of subjectPublicKeyInfo, as specified in [RFC5280], and exactData set to true.

When this specification says to parse a PrivateKeyInfo, the user agent must parse an ASN.1 structure with data set to the sequence of bytes to be parsed, structure as the ASN.1 structure of PrivateKeyInfo, as specified in [RFC5208], and exactData set to true.

When this specification says to parse a JWK, the user agent must run the following steps:

Let data be the sequence of bytes to be parsed.
Let json be the Unicode string that results from interpreting data according to UTF-8.
Convert json to UTF-16.
Let result be the object literal that results from executing the JSON.parse internal function in the context of a new global object, with text argument set to a JavaScript String containing json.
Let key be the result of converting result to the IDL dictionary type of JsonWebKey.
If the kty field of key is not defined, then throw a DataError.
Return key.

When this specification says to calculate the usage intersection of two sequences, a and b the result shall be a sequence containing each recognized key usage value that appears in both a and b, in the order listed in the list of recognized key usage values, where a value is said to appear in a sequence if an element of the sequence exists that is a case-sensitive string match for that value.

When this specification says to calculate the normalized value of a usages list, usages the result shall be the usage intersection of usages and a sequence containing all recognized key usage values.

When this specification refers to the cached ECMAScript object associated with an internal slot [[slot]] of object, the user agent must run the following steps:

If the [[slot_cached]] internal slot of object is undefined:

Set the [[slot_cached]] internal slot of object to the result of performing type conversion to an ECMAScript object as defined in [WebIDL] to the contents of the [[slot]] internal slot of object.
Return the contents of the [[slot_cached]] internal slot of object.

The Crypto interface represents an interface to general purpose cryptographic functionality including a cryptographically strong pseudo-random number generator seeded with truly random values.

WebIDLpartial interface mixin WindowOrWorkerGlobalScope {
  [SameObject] readonly attribute Crypto crypto;
};

[Exposed=(Window,Worker)]
interface Crypto {
  [SecureContext] readonly attribute SubtleCrypto subtle;
  ArrayBufferView getRandomValues(ArrayBufferView array);
  [SecureContext] DOMString randomUUID();
};

Note

Implementations should generate cryptographically strong random values using well-established cryptographic pseudo-random number generators seeded with high-quality entropy, such as from an operating-system entropy source (e.g., "/dev/urandom"). This specification provides no lower-bound on the information theoretic entropy present in cryptographically strong random values, but implementations should make a best effort to provide as much entropy as practicable.

Note

This interface defines a synchronous method for obtaining cryptographically strong random values. While some devices and implementations may support truly random cryptographic number generators or provide interfaces that block when there is insufficient entropy, implementations are discouraged from using these sources when implementing getRandomValues, both for performance and to avoid depleting the system of entropy. Instead, these sources should be used to seed a cryptographic pseudo-random number generator that can then return suitable values efficiently.

The getRandomValues method generates cryptographically strong random values. It must act as follows:

If array is not an Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array, then throw a TypeMismatchError and terminate the algorithm.
Let byteLength be the byte length of array.
If byteLength is greater than 65536, throw a QuotaExceededError and terminate the algorithm.
Let bytes be a byte sequence of length byteLength.
Fill bytes with cryptographically secure random bytes.
Write bytes into array.
Return array.

Note

Do not generate keys using the getRandomValues method. Use the generateKey method instead.

The randomUUID method generates a new version 4 UUID and returns its namespace specific string representation as described in section 3 of [RFC4122]. To generate a random UUID:

Let bytes be a byte sequence of length 16.
Fill bytes with cryptographically secure random bytes.
Set the 4 most significant bits of bytes[6], which represent the UUID version, to 0100.
Set the 2 most significant bits of bytes[8], which represent the UUID variant, to 10.
Return the string concatenation of «
1. hexadecimal representation of bytes[0], hexadecimal representation of bytes[1], hexadecimal representation of bytes[2], hexadecimal representation of bytes[3],
2. "-",
3. hexadecimal representation of bytes[4], hexadecimal representation of bytes[5],
4. "-",
5. hexadecimal representation of bytes[6], hexadecimal representation of bytes[7],
6. "-",
7. hexadecimal representation of bytes[8], hexadecimal representation of bytes[9],
8. "-",
9. hexadecimal representation of bytes[10], hexadecimal representation of bytes[11], hexadecimal representation of bytes[12], hexadecimal representation of bytes[13], hexadecimal representation of bytes[14], hexadecimal representation of bytes[15]
».

For the steps described in the algorithm to generate a random UUID, the hexadecimal representation of a byte value is the two-character string created by expressing value in hexadecimal using ASCII lower hex digits, left-padded with "0" to reach two ASCII lower hex digits.

The subtle attribute provides an instance of the SubtleCrypto interface which provides low-level cryptographic primitives and algorithms.

The Algorithm object is a dictionary object [WEBIDL] which is used to specify an algorithm and any additional parameters required to fully specify the desired operation.

WebIDLtypedef (object or DOMString) AlgorithmIdentifier;

typedef AlgorithmIdentifier HashAlgorithmIdentifier;

dictionary Algorithm {
  required DOMString name;
};

name: The name of the registered algorithm to use.

The KeyAlgorithm dictionary represents information about the contents of a given CryptoKey object.

WebIDLdictionary KeyAlgorithm {
  required DOMString name;
};

This section is non-normative.

The KeyAlgorithm dictionary is provided to aid in documenting how fixed, public properties of a CryptoKey are reflected back to an application. The actual dictionary type is never exposed to applications.

name: The name of the algorithm used to generate the CryptoKey

The CryptoKey object represents an opaque reference to keying material that is managed by the user agent.

WebIDLenum KeyType { "public", "private", "secret" };

enum KeyUsage { "encrypt", "decrypt", "sign", "verify", "deriveKey", "deriveBits", "wrapKey", "unwrapKey" };

[SecureContext,Exposed=(Window,Worker),Serializable]
interface CryptoKey {
  readonly attribute KeyType type;
  readonly attribute boolean extractable;
  readonly attribute object algorithm;
  readonly attribute object usages;
};

This section is non-normative.

This specification provides a uniform interface for many different kinds of keying material managed by the user agent. This may include keys that have been generated by the user agent, derived from other keys by the user agent, imported to the user agent through user actions or using this API, pre-provisioned within software or hardware to which the user agent has access or made available to the user agent in other ways. The term key refers broadly to any keying material including actual keys for cryptographic operations and secret values obtained within key derivation or exchange operations.

The CryptoKey object is not required to directly interface with the underlying key storage mechanism, and may instead simply be a reference for the user agent to understand how to obtain the keying material when needed, e.g. when performing a cryptographic operation.

KeyType: The type of a key. The recognized key type values are "public", "private" and "secret". Opaque keying material, including that used for symmetric algorithms, is represented by secret, while keys used as part of asymmetric algorithms composed of public/private keypairs will be either public or private.
KeyUsage: A type of operation that may be performed using a key. The recognized key usage values are encrypt, decrypt, sign, verify, deriveKey, deriveBits, wrapKey and unwrapKey.

Every CryptoKey object has a set of internal slots that store information about the key. These slots are not exposed as part of this specification; they represent internal state that an implementation uses to implement this specification. The notational convention used in [ECMA-262] is re-used here; internal slots are identified by names enclosed in double square brackets [[ ]].

All CryptoKey objects have internal slots named [[type]], [[extractable]], [[algorithm]], [[algorithm_cached]], [[usages]], [[usages_cached]], and [[handle]].

The contents of the [[algorithm]] internal slot shall be, or be derived from, a KeyAlgorithm. The contents of the [[usages]] internal slot shall be of type Sequence<KeyUsage>.

Note

The [[handle]] slot is an opaque type that contains whatever data the underlying cryptographic implementation uses to represent a logical key. Different cryptographic implementations may use different types, ranging from opaque identifiers represented as integers, pointer types, or structures that provide identifying information. These handles are never exposed to applications.

type: Reflects the [[type]] internal slot, which contains the type of the underlying key.
extractable: Reflects the [[extractable]] internal slot, which indicates whether or not the raw keying material may be exported by the application.
algorithm: Returns the cached ECMAScript object associated with the [[algorithm]] internal slot.
usages: Returns the cached ECMAScript object associated with the [[usages]] internal slot, which indicates which cryptographic operations are permissible to be used with this key.

CryptoKey objects are serializable objects. Their serialization steps, given value and serialized, are:

Set serialized.[[Type]] to the [[type]] internal slot of value.
Set serialized.[[Extractable]] to the [[extractable]] internal slot of value.
Set serialized.[[Algorithm]] to the sub-serialization of the [[algorithm]] internal slot of value.
Set serialized.[[Usages]] to the sub-serialization of the [[usages]] internal slot of value.
Set serialized.[[Handle]] to the [[handle]] internal slot of value.

Their deserialization steps, given serialized and value, are:

Initialize the [[type]] internal slot of value to serialized.[[Type]].
Initialize the [[extractable]] internal slot of value to serialized.[[Extractable]].
Initialize the [[algorithm]] internal slot of value to the sub-deserialization of serialized.[[Algorithm]].
Initialize the [[usages]] internal slot of value to the sub-deserialization of serialized.[[Usages]].
Initialize the [[handle]] internal slot of value to serialized.[[Handle]].

Note

When deserializing a serialized CryptoKey object, it is important that the object is not deserialized as a different type. This is normatively required by the definition of the deserialization steps, but it merits specific attention, as such deserialization may expose the contents of the key material, which in some cases (such as when the [[extractable]] internal slot is false) should not be exposed to applications.

The SubtleCrypto interface provides a set of methods for dealing with low-level cryptographic primitives and algorithms.

WebIDLenum KeyFormat { "raw", "spki", "pkcs8", "jwk" };

[SecureContext,Exposed=(Window,Worker)]
interface SubtleCrypto {
  Promise<ArrayBuffer> encrypt(
    AlgorithmIdentifier algorithm,
    CryptoKey key,
    BufferSource data
  );
  Promise<ArrayBuffer> decrypt(
    AlgorithmIdentifier algorithm,
    CryptoKey key,
    BufferSource data
  );
  Promise<ArrayBuffer> sign(
    AlgorithmIdentifier algorithm,
    CryptoKey key,
    BufferSource data
  );
  Promise<boolean> verify(
    AlgorithmIdentifier algorithm,
    CryptoKey key,
    BufferSource signature,
    BufferSource data
  );
  Promise<ArrayBuffer> digest(
    AlgorithmIdentifier algorithm,
    BufferSource data
  );

  Promise<(CryptoKey or CryptoKeyPair)> generateKey(
    AlgorithmIdentifier algorithm,
    boolean extractable,
    sequence<KeyUsage> keyUsages
  );
  Promise<CryptoKey> deriveKey(
    AlgorithmIdentifier algorithm,
    CryptoKey baseKey,
    AlgorithmIdentifier derivedKeyType,
    boolean extractable,
    sequence<KeyUsage> keyUsages
  );
  Promise<ArrayBuffer> deriveBits(
    AlgorithmIdentifier algorithm,
    CryptoKey baseKey,
    optional unsigned long? length = null
  );

  Promise<CryptoKey> importKey(
    KeyFormat format,
    (BufferSource or JsonWebKey) keyData,
    AlgorithmIdentifier algorithm,
    boolean extractable,
    sequence<KeyUsage> keyUsages
  );
  Promise<(ArrayBuffer or JsonWebKey)> exportKey(
    KeyFormat format,
    CryptoKey key
  );

  Promise<ArrayBuffer> wrapKey(
    KeyFormat format,
    CryptoKey key,
    CryptoKey wrappingKey,
    AlgorithmIdentifier wrapAlgorithm
  );
  Promise<CryptoKey> unwrapKey(
    KeyFormat format,
    BufferSource wrappedKey,
    CryptoKey unwrappingKey,
    AlgorithmIdentifier unwrapAlgorithm,
    AlgorithmIdentifier unwrappedKeyAlgorithm,
    boolean extractable,
    sequence<KeyUsage> keyUsages
  );
};

Note

The SubtleCrypto interface is named "SubtleCrypto" to reflect the fact that many of these algorithms have subtle usage requirements in order to provide the required algorithmic security guarantees.

For example, the direct use of an unauthenticated encryption scheme, such as AES in counter mode, gives potential attackers the ability to manipulate bits in the output by manipulating bits in the input, compromising the integrity of the message. However, AES-CTR can be used securely in combination with other cryptographic primitives, such as message authentication codes, to ensure the integrity of the protected message, but only when the message authentication code is constructed over the encrypted message and IV.

Developers making use of the SubtleCrypto interface are expected to be aware of the security concerns associated with both the design and implementation of the various algorithms provided. The raw algorithms are provided in order to allow developers maximum flexibility in implementing a variety of protocols and applications, each of which may represent the composition and security parameters in a unique manner that necessitate the use of the raw algorithms.

KeyFormat

Specifies a serialization format for a key. The recognized key format values are:

raw: An unformatted sequence of bytes. Intended for secret keys.
pkcs8: The DER encoding of the PrivateKeyInfo structure from [RFC5208].
spki: The DER encoding of the SubjectPublicKeyInfo structure from [RFC5280].
jwk: The key is a JsonWebKey dictionary encoded as a JavaScript object

The crypto task source: This task source is used to queue tasks to resolve or reject promises created in response to calls to methods of SubtleCrypto.

Note

This specification makes no specific requirements on the ordering of responses to calls to methods of SubtleCrypto, neither between multiple calls, nor between calls and tasks from other task sources. This task source is merely used to queue a task to resolve or reject the relevant promise whenever the cryptographic operation is completed, in order to prevent race conditions.

Note

All errors are reported asynchronously by rejecting the returned Promise. This includes Web IDL type mapping errors.

The encrypt method returns a new Promise object that will encrypt data using the specified AlgorithmIdentifier with the supplied CryptoKey. It must act as follows:

Let algorithm and key be the algorithm and key parameters passed to the encrypt() method, respectively.
Let data be the result of getting a copy of the bytes held by the data parameter passed to the encrypt() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "encrypt".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of key then throw an InvalidAccessError.
If the [[usages]] internal slot of key does not contain an entry that is "encrypt", then throw an InvalidAccessError.
Let ciphertext be the result of performing the encrypt operation specified by normalizedAlgorithm using algorithm and key and with data as plaintext.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing ciphertext.
Resolve promise with result.

The decrypt method returns a new Promise object that will decrypt data using the specified AlgorithmIdentifier with the supplied CryptoKey. It must act as follows:

Let algorithm and key be the algorithm and key parameters passed to the decrypt() method, respectively.
Let data be the result of getting a copy of the bytes held by the data parameter passed to the decrypt() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "decrypt".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of key then throw an InvalidAccessError.
If the [[usages]] internal slot of key does not contain an entry that is "decrypt", then throw an InvalidAccessError.
Let plaintext be the result of performing the decrypt operation specified by normalizedAlgorithm using key and algorithm and with data as ciphertext.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing plaintext.
Resolve promise with result.

The sign method returns a new Promise object that will sign data using the specified AlgorithmIdentifier with the supplied CryptoKey. It must act as follows:

Let algorithm and key be the algorithm and key parameters passed to the sign() method, respectively.
Let data be the result of getting a copy of the bytes held by the data parameter passed to the sign() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "sign".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of key then throw an InvalidAccessError.
If the [[usages]] internal slot of key does not contain an entry that is "sign", then throw an InvalidAccessError.
Let signature be the result of performing the sign operation specified by normalizedAlgorithm using key and algorithm and with data as message.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing signature.
Resolve promise with result.

The verify method returns a new Promise object that will verify data using the specified AlgorithmIdentifier with the supplied CryptoKey. It must act as follows:

Let algorithm and key be the algorithm and key parameters passed to the verify() method, respectively.
Let signature be the result of getting a copy of the bytes held by the signature parameter passed to the verify() method.
Let data be the result of getting a copy of the bytes held by the data parameter passed to the verify() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "verify".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of key then throw an InvalidAccessError.
If the [[usages]] internal slot of key does not contain an entry that is "verify", then throw an InvalidAccessError.
Let result be the result of performing the verify operation specified by normalizedAlgorithm using key, algorithm and signature and with data as message.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Resolve promise with result.

The digest method returns a new Promise object that will digest data using the specified AlgorithmIdentifier. It must act as follows:

Let algorithm be the algorithm parameter passed to the digest() method.
Let data be the result of getting a copy of the bytes held by the data parameter passed to the digest() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "digest".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
Let digest be the result of performing the digest operation specified by normalizedAlgorithm using algorithm, with data as message.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing digest.
Resolve promise with result.

When invoked, generateKey MUST perform the following steps:

Let algorithm, extractable and usages be the algorithm, extractable and keyUsages parameters passed to the generateKey() method, respectively.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "generateKey".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
Let result be the result of performing the generate key operation specified by normalizedAlgorithm using algorithm, extractable and usages.
If result is a CryptoKey object:

If the [[type]] internal slot of result is "secret" or "private" and usages is empty, then throw a SyntaxError.

If result is a CryptoKeyPair object:

If the [[usages]] internal slot of the privateKey attribute of result is the empty sequence, then throw a SyntaxError.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of converting result to an ECMAScript Object in realm, as defined by [WebIDL].
Resolve promise with result.

When invoked, deriveKey MUST perform the following steps:

Let algorithm, baseKey, derivedKeyType, extractable and usages be the algorithm, baseKey, derivedKeyType, extractable and keyUsages parameters passed to the deriveKey() method, respectively.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "deriveBits".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let normalizedDerivedKeyAlgorithmImport be the result of normalizing an algorithm, with alg set to derivedKeyType and op set to "importKey".
If an error occurred, return a Promise rejected with normalizedDerivedKeyAlgorithmImport.
Let normalizedDerivedKeyAlgorithmLength be the result of normalizing an algorithm, with alg set to derivedKeyType and op set to "get key length".
If an error occurred, return a Promise rejected with normalizedDerivedKeyAlgorithmLength.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of baseKey then throw an InvalidAccessError.
If the [[usages]] internal slot of baseKey does not contain an entry that is "deriveKey", then throw an InvalidAccessError.
Let length be the result of performing the get key length algorithm specified by normalizedDerivedKeyAlgorithmLength using derivedKeyType.
Let secret be the result of performing the derive bits operation specified by normalizedAlgorithm using key, algorithm and length.
Let result be the result of performing the import key operation specified by normalizedDerivedKeyAlgorithmImport using "raw" as format, secret as keyData, derivedKeyType as algorithm and using extractable and usages.
If the [[type]] internal slot of result is "secret" or "private" and usages is empty, then throw a SyntaxError.
Set the [[extractable]] internal slot of result to extractable.
Set the [[usages]] internal slot of result to the normalized value of usages.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of converting result to an ECMAScript Object in realm, as defined by [WebIDL].
Resolve promise with result.

When invoked, deriveBits MUST perform the following steps:

Let algorithm, baseKey and length, be the algorithm, baseKey and length parameters passed to the deriveBits() method, respectively.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "deriveBits".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of baseKey then throw an InvalidAccessError.
If the [[usages]] internal slot of baseKey does not contain an entry that is "deriveBits", then throw an InvalidAccessError.
Let bits be the result of performing the derive bits operation specified by normalizedAlgorithm using baseKey, algorithm and length.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing bits.
Resolve promise with result.

When invoked, the importKey method MUST perform the following steps:

Let format, algorithm, extractable and usages, be the format, algorithm, extractable and keyUsages parameters passed to the importKey() method, respectively.
If format is equal to the string "raw", "pkcs8", or "spki":
1. If the keyData parameter passed to the importKey() method is a JsonWebKey dictionary, throw a TypeError.
2. Let keyData be the result of getting a copy of the bytes held by the keyData parameter passed to the importKey() method.
If format is equal to the string "jwk":
1. If the keyData parameter passed to the importKey() method is not a JsonWebKey dictionary, throw a TypeError.
2. Let keyData be the keyData parameter passed to the importKey() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "importKey".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
Let result be the CryptoKey object that results from performing the import key operation specified by normalizedAlgorithm using keyData, algorithm, format, extractable and usages.
If the [[type]] internal slot of result is "secret" or "private" and usages is empty, then throw a SyntaxError.
Set the [[extractable]] internal slot of result to extractable.
Set the [[usages]] internal slot of result to the normalized value of usages.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of converting result to an ECMAScript Object in realm, as defined by [WebIDL].
Resolve promise with result.

Note

Support of "raw" key formats is encouraged for interoperability. Web developers should consult the test-suite for detailed information on implementations support of other key formats.

Note

For structured key formats, "spki", "pkcs8" and "jwk", fields that are not explicitly referred to in the key import procedures for an algorithm are ignored.

When invoked, the exportKey method MUST perform the following steps:

Let format and key be the format and key parameters passed to the exportKey() method, respectively.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of the [[algorithm]] internal slot of key does not identify a registered algorithm that supports the export key operation, then throw a NotSupportedError.
If the [[extractable]] internal slot of key is false, then throw an InvalidAccessError.
Let result be the result of performing the export key operation specified by the [[algorithm]] internal slot of key using key and format.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
If format is equal to the strings "raw", "pkcs8", or "spki":

Let result be the result of creating an ArrayBuffer in realm, containing result.

If format is equal to the string "jwk":

Let result be the result of converting result to an ECMAScript Object in realm, as defined by [WebIDL].
Resolve promise with result.

Note

Support of "raw" key formats is encouraged for interoperability. Web developers should consult the test-suite for detailed information on implementations support of other key formats.

When invoked, the wrapKey method MUST perform the following steps:

Let format, key, wrappingKey and algorithm be the format, key, wrappingKey and wrapAlgorithm parameters passed to the wrapKey() method, respectively.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "wrapKey".
If an error occurred, let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "encrypt".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of wrappingKey then throw an InvalidAccessError.
If the [[usages]] internal slot of wrappingKey does not contain an entry that is "wrapKey", then throw an InvalidAccessError.
If the algorithm identified by the [[algorithm]] internal slot of key does not support the export key operation, then throw a NotSupportedError.
If the [[extractable]] internal slot of key is false, then throw an InvalidAccessError.

Note

Because the wrapKey method effectively exports the key, only keys marked as extractable may be wrapped. In particular, this means that this API cannot create a wrapped JWK key that is marked as non-extractable using the ext JWK member.

However, the unwrapKey method does support the ext JWK member, so that wrapped non-extractable keys created elsewhere, for example by a server, can be unwrapped using this API.
Let exportedKey be the result of performing the export key operation specified by the [[algorithm]] internal slot of key using key and format.
If format is equal to the strings "raw", "pkcs8", or "spki":

Let bytes be exportedKey.

If format is equal to the string "jwk":
1. Let json be the result of representing exportedKey as a UTF-16 string conforming to the JSON grammar; for example, by executing the JSON.stringify algorithm specified in [ECMA-262] in the context of a new global object.
2. Let bytes be the result of UTF-8 encoding json.
Note

The key wrapping operations for some algorithms place constraints on the payload size. For example AES-KW requires the payload to be a multiple of 8 bytes in length and RSA-OAEP places a restriction on the length. For key formats that offer flexibility in serialization of a given key (for example JWK), implementations may choose to adapt the serialization to the constraints of the wrapping algorithm. This is why JSON.stringify is not normatively required, as otherwise it would prohibit implementations from introducing added padding.
If normalizedAlgorithm supports the wrap key operation:

Let result be the result of performing the wrap key operation specified by normalizedAlgorithm using algorithm, wrappingKey as key and bytes as plaintext.

Otherwise, if normalizedAlgorithm supports the encrypt operation:

Let result be the result of performing the encrypt operation specified by normalizedAlgorithm using algorithm, wrappingKey as key and bytes as plaintext.

Otherwise:

throw a NotSupportedError.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of creating an ArrayBuffer in realm, containing result.
Resolve promise with result.

Note

Support of "raw" key formats is encouraged for interoperability. Web developers should consult the test-suite for detailed information on implementations support of other key formats.

When invoked, the unwrapKey method MUST perform the following steps:

Let format, unwrappingKey, algorithm, unwrappedKeyAlgorithm, extractable and usages, be the format, unwrappingKey, unwrapAlgorithm, unwrappedKeyAlgorithm, extractable and keyUsages parameters passed to the unwrapKey() method, respectively.
Let wrappedKey be the result of getting a copy of the bytes held by the wrappedKey parameter passed to the unwrapKey() method.
Let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "unwrapKey".
If an error occurred, let normalizedAlgorithm be the result of normalizing an algorithm, with alg set to algorithm and op set to "decrypt".
If an error occurred, return a Promise rejected with normalizedAlgorithm.
Let normalizedKeyAlgorithm be the result of normalizing an algorithm, with alg set to unwrappedKeyAlgorithm and op set to "importKey".
If an error occurred, return a Promise rejected with normalizedKeyAlgorithm.
Let realm be the relevant realm of this.
Let promise be a new Promise.
Return promise and perform the remaining steps in parallel.
If the following steps or referenced procedures say to throw an error, queue a global task on the crypto task source, given realm's global object, to reject promise with the returned error; and then terminate the algorithm.
If the name member of normalizedAlgorithm is not equal to the name attribute of the [[algorithm]] internal slot of unwrappingKey then throw an InvalidAccessError.
If the [[usages]] internal slot of unwrappingKey does not contain an entry that is "unwrapKey", then throw an InvalidAccessError.
If normalizedAlgorithm supports an unwrap key operation:

Let bytes be the result of performing the unwrap key operation specified by normalizedAlgorithm using algorithm, unwrappingKey as key and wrappedKey as ciphertext.

Otherwise, if normalizedAlgorithm supports a decrypt operation:

Let bytes be the result of performing the decrypt operation specified by normalizedAlgorithm using algorithm, unwrappingKey as key and wrappedKey as ciphertext.

Otherwise:

throw a NotSupportedError.
If format is equal to the strings "raw", "pkcs8", or "spki":

Let key be bytes.

If format is equal to the string "jwk":

Let key be the result of executing the parse a JWK algorithm, with bytes as the data to be parsed.
Let result be the result of performing the import key operation specified by normalizedKeyAlgorithm using unwrappedKeyAlgorithm as algorithm, format, usages and extractable and with key as keyData.
If the [[type]] internal slot of result is "secret" or "private" and usages is empty, then throw a SyntaxError.
Set the [[extractable]] internal slot of result to extractable.
Set the [[usages]] internal slot of result to the normalized value of usages.
Queue a global task on the crypto task source, given realm's global object, to perform the remaining steps.
Let result be the result of converting result to an ECMAScript Object in realm, as defined by [WebIDL].
Resolve promise with result.

Note

Support of "raw" key formats is encouraged for interoperability. Web developers should consult the test-suite for detailed information on implementations support of other key formats.

The methods of the SubtleCrypto interface return errors by rejecting the returned promise with a predefined exception defined in ECMAScript [ECMA-262] or DOMException. The following predefined exceptions are used: TypeError. The following DOMException types from [DOM] are used:

Name	Description
`NotSupportedError`	The algorithm is not supported
`SyntaxError`	A required parameter was missing or out-of-range
`InvalidAccessError`	The requested operation is not valid for the provided key
`DataError`	Data provided to an operation does not meet requirements
`OperationError`	The operation failed for an operation-specific reason

When this specification says to throw an error, the user agent must throw an error as described in [WebIDL]. When this occurs in a sub-algorithm, this results in termination of execution of the sub-algorithm and all ancestor algorithms until one is reached that explicitly describes procedures for catching exceptions. The error object thrown shall be associated with the relevant realm of this.

WebIDLdictionary RsaOtherPrimesInfo {
  // The following fields are defined in Section 6.3.2.7 of JSON Web Algorithms
  DOMString r;
  DOMString d;
  DOMString t;
};

dictionary JsonWebKey {
  // The following fields are defined in Section 3.1 of JSON Web Key
  DOMString kty;
  DOMString use;
  sequence<DOMString> key_ops;
  DOMString alg;

  // The following fields are defined in JSON Web Key Parameters Registration
  boolean ext;

  // The following fields are defined in Section 6 of JSON Web Algorithms
  DOMString crv;
  DOMString x;
  DOMString y;
  DOMString d;
  DOMString n;
  DOMString e;
  DOMString p;
  DOMString q;
  DOMString dp;
  DOMString dq;
  DOMString qi;
  sequence<RsaOtherPrimesInfo> oth;
  DOMString k;
};

The JsonWebKey dictionary provides a way to represent and exchange cryptographic keys represented by the JSON Web Key [JWK] structure, while allowing native and efficient use within Web Cryptography API applications.

The members of the RsaOtherPrimesInfo are defined in Section 6.3.2.7 of JSON Web Algorithms.

WebIDLtypedef Uint8Array BigInteger;

The BigInteger typedef is a Uint8Array that holds an arbitrary magnitude unsigned integer in big-endian order. Values read from the API SHALL have minimal typed array length (that is, at most 7 leading zero bits, except the value 0 which shall have length 8 bits). The API SHALL accept values with any number of leading zero bits, including the empty array, which represents zero.

Note

Since the integer is unsigned, the highest order bit is NOT a sign bit. Implementors should take care when mapping to big integer implementations that expected signed integers.

WebIDLdictionary CryptoKeyPair {
  CryptoKey publicKey;
  CryptoKey privateKey;
};

The CryptoKeyPair dictionary represents an asymmetric key pair that is comprised of both public (publicKey) and private (privateKey) keys.

This section is non-normative.

In addition to providing a common interface to perform cryptographic operations, by way of the SubtleCrypto interface, this specification also provides descriptions for a variety of algorithms that authors may wish to use and that User Agents may choose to implement. This includes a selection of commonly-deployed symmetric and asymmetric algorithms, key derivation mechanisms, and methods for wrapping and unwrapping keys. Further, this specification defines a process to allow additional specifications to introduce additional cryptographic algorithms.

Every cryptographic algorithm defined for use with the Web Cryptography API MUST have a unique name, referred to as its recognized algorithm name, such that no other specification defines the same case-insensitive string for use with the Web Cryptography API.

Every cryptographic algorithm defined for use with the Web Cryptography API has a list of supported operations, which are a set of sub-algorithms to be invoked by the SubtleCrypto interface in order to perform the desired cryptographic operation. This specification makes use of the following operations:

encrypt
decrypt
sign
verify
digest
deriveBits
wrapKey
unwrapKey
generateKey
importKey
exportKey
get key length

If a given algorithm specification does not list a particular operation as supported, or explicitly lists an operation as not-supported, then the User Agent MUST behave as if the invocation of the sub-algorithm threw a NotSupportedError.

Every cryptographic algorithm defined for use with the Web Cryptography API MUST define, for every supported operation, the IDL type to use for algorithm normalization, as well as the IDL type or types of the return values of the sub-algorithms.

Every cryptographic algorithm definition within this specification employs the following specification conventions. A section, titled "Registration", will include the recognized algorithm name. Additionally, it includes a table, which will list each of the supported operations as rows, identified by the Operation column. The contents of the Parameters column for a given row will contain the IDL type to use for algorithm normalization for that operation, and the contents of the Result column for that row indicate the IDL type that results from performing the supported operation.

If a conforming User Agent implements an algorithm, it MUST implement all of the supported operations and MUST return the IDL type specified.

Additionally, upon initialization, conforming User Agents must perform the define an algorithm steps for each of the supported operations, registering their IDL parameter type as indicated.

Unless otherwise stated, objects created by the operations defined in this specification shall be associated with the relevant realm of this.

This section is non-normative.

The AlgorithmIdentifier typedef permits algorithms to either be specified as a DOMString or an object. The usage of DOMString is to permit authors a short-hand for noting algorithms that have no parameters (e.g. SHA-1). The usage of object is to allow an Algorithm (or appropriate subclass) to be specified, which contains all of the associated parameters for an object.

Because of this, it's necessary to define the algorithm for converting an AlgorithmIdentifier into an appropriate dictionary that is usable with this API. This algorithm must be extensible, so as to allow new cryptographic algorithms to be added, and consistent, so that Web IDL type mapping can occur before any control is returned to the calling script, which would potentially allow the mutation of parameters or the script environment.

This specification makes use of an internal object, supportedAlgorithms. This internal object is not exposed to applications.

Because this value is not exposed to applications, the exact type is not specified. It is only required to behave as an associative container of key/value pairs, where comparisons of keys are performed in a case-sensitive manner.

The initial contents of this internal object are as follows:

For each value, v in the List of supported operations, set the v key of the internal object supportedAlgorithms to a new associative container.

The define an algorithm algorithm is used by specification authors to indicate how a user agent should normalize arguments for a particular algorithm. Its input is an algorithm name alg, represented as a DOMString, operation name op, represented as a DOMString, and desired IDL dictionary type type. The algorithm behaves as follows:

Let registeredAlgorithms be the associative container stored at the op key of supportedAlgorithms.
Set the alg key of registeredAlgorithms to the IDL dictionary type type.

The normalize an algorithm algorithm defines a process for coercing inputs to a targeted IDL dictionary type, after Web IDL conversion has occurred. It is designed to be extensible, to allow future specifications to define additional algorithms, as well as safe for use with Promises. Its input is an operation name op and an AlgorithmIdentifier alg. Its output is either an IDL dictionary type or an error. It behaves as follows:

If alg is an instance of a DOMString:

Return the result of running the normalize an algorithm algorithm, with the alg set to a new Algorithm dictionary whose name attribute is alg, and with the op set to op.

If alg is an object:

Let registeredAlgorithms be the associative container stored at the op key of supportedAlgorithms.
Let initialAlg be the result of converting the ECMAScript object represented by alg to the IDL dictionary type Algorithm, as defined by [WebIDL].
If an error occurred, return the error and terminate this algorithm.
Let algName be the value of the name attribute of initialAlg.
If registeredAlgorithms contains a key that is a case-insensitive string match for algName:
1. Set algName to the value of the matching key.
2. Let desiredType be the IDL dictionary type stored at algName in registeredAlgorithms.
Otherwise:

Return a new NotSupportedError and terminate this algorithm.
Let normalizedAlgorithm be the result of converting the ECMAScript object represented by alg to the IDL dictionary type desiredType, as defined by [WebIDL].
Set the name attribute of normalizedAlgorithm to algName.
If an error occurred, return the error and terminate this algorithm.
Let dictionaries be a list consisting of the IDL dictionary type desiredType and all of desiredType's inherited dictionaries, in order from least to most derived.
For each dictionary dictionary in dictionaries:
1. For each dictionary member member declared on dictionary, in order:
  1. Let key be the identifier of member.
  2. Let idlValue be the value of the dictionary member with key name of key on normalizedAlgorithm.
  3. If member is of the type BufferSource and is present:
    
    Set the dictionary member on normalizedAlgorithm with key name key to the result of getting a copy of the bytes held by idlValue, replacing the current value.
    
    If member is of the type HashAlgorithmIdentifier:
    
    Set the dictionary member on normalizedAlgorithm with key name key to the result of normalizing an algorithm, with the alg set to idlValue and the op set to "digest".
    
    If member is of the type AlgorithmIdentifier:
    
    Set the dictionary member on normalizedAlgorithm with key name key to the result of normalizing an algorithm, with the alg set to idlValue and the op set to the operation defined by the specification that defines the algorithm identified by algName.
  4. If an error occurred, return the error and terminate this algorithm.
Return normalizedAlgorithm.

This section is non-normative.

As this API is meant to be extensible, in order to keep up with future developments within cryptography, there are no algorithms that conforming user agents are required to implement. As such, authors should check to see what algorithms are currently recommended and supported by implementations.

As highlighted in the Security Considerations, even cryptographic algorithms that might be considered strong for one purpose may be insufficient when used with another purpose. Authors should therefore proceed with extreme caution before inventing new cryptographic protocols.

Additionally, this specification includes several algorithms which, in their default usage, can result in cryptographic vulnerabilities. While these concerns may be mitigated, such as through the combination and composition with additional algorithms provided by this specification, authors should proceed with caution and review the relevant cryptographic literature before using a given algorithm. The inclusion of algorithms within this specification is not an indicator of their suitability for any or all purpose, and instead merely serve to provide as a specification for how a conforming User Agent must implement the given algorithm, if it choses to implement the algorithm.

In order to promote interoperability for developers, this specification includes a list of suggested algorithms. These are considered to be the most widely used algorithms in practice at the time of writing, and therefore provide a good starting point for initial implementations of this specification. The suggested algorithms are:

HMAC using SHA-1
HMAC using SHA-256
RSASSA-PKCS1-v1_5 using SHA-1
RSA-PSS using SHA-256 and MGF1 with SHA-256.
RSA-OAEP using SHA-256 and MGF1 with SHA-256.
ECDSA using P-256 curve and SHA-256
AES-CBC

This section is non-normative.

The "RSASSA-PKCS1-v1_5" algorithm identifier is used to perform signing and verification using the RSASSA-PKCS1-v1_5 algorithm specified in [RFC3447] and using the SHA hash functions defined in this specification.

Other specifications may specify the use of additional hash algorithms with RSASSA-PKCS1-v1_5. Such specifications must define the digest operations for the additional hash algorithms and key import steps and key export steps for RSASSA-PKCS1-v1_5.

The recognized algorithm name for this algorithm is "RSASSA-PKCS1-v1_5".

Operation	Parameters	Result
sign	None	byte sequence
verify	None	boolean
generateKey	`RsaHashedKeyGenParams`	`CryptoKeyPair`
importKey	`RsaHashedImportParams`	`CryptoKey`
exportKey	None	object

WebIDLdictionary RsaKeyGenParams : Algorithm {
  required [EnforceRange] unsigned long modulusLength;
  required BigInteger publicExponent;
};

The modulusLength member contains the length, in bits, of the RSA modulus.

The publicExponent member contains the RSA public exponent.

WebIDLdictionary RsaHashedKeyGenParams : RsaKeyGenParams {
  required HashAlgorithmIdentifier hash;
};

The hash member represents the hash algorithm to use.

WebIDLdictionary RsaKeyAlgorithm : KeyAlgorithm {
  required unsigned long modulusLength;
  required BigInteger publicExponent;
};

The modulusLength member contains the length, in bits, of the RSA modulus.

The publicExponent member contains the RSA public exponent.

WebIDLdictionary RsaHashedKeyAlgorithm : RsaKeyAlgorithm {
  required KeyAlgorithm hash;
};

The hash member describes the hash algorithm that is used with this key.

WebIDLdictionary RsaHashedImportParams : Algorithm {
  required HashAlgorithmIdentifier hash;
};

The hash member describes the hash algorithm to use.

If the [[type]] internal slot of key is not "private", then throw an InvalidAccessError.
Perform the signature generation operation defined in Section 8.2 of [RFC3447] with the key represented by the [[handle]] internal slot of key as the signer's private key and message as M and using the hash function specified in the hash attribute of the [[algorithm]] internal slot of key as the Hash option for the EMSA-PKCS1-v1_5 encoding method.
If performing the operation results in an error, then throw an OperationError.
Let signature be the value S that results from performing the operation.
Return signature.

If the [[type]] internal slot of key is not "public", then throw an InvalidAccessError.
Perform the signature verification operation defined in Section 8.2 of [RFC3447] with the key represented by the [[handle]] internal slot of key as the signer's RSA public key and message as M and signature as S and using the hash function specified in the hash attribute of the [[algorithm]] internal slot of key as the Hash option for the EMSA-PKCS1-v1_5 encoding method.
Let result be a boolean with value true if the result of the operation was "valid signature" and the value false otherwise.
Return result.

If usages contains an entry which is not "sign" or "verify", then throw a SyntaxError.
Generate an RSA key pair, as defined in [RFC3447], with RSA modulus length equal to the modulusLength attribute of normalizedAlgorithm and RSA public exponent equal to the publicExponent attribute of normalizedAlgorithm.
If generation of the key pair fails, then throw an OperationError.
Let algorithm be a new RsaHashedKeyAlgorithm dictionary.
Set the name attribute of algorithm to "RSASSA-PKCS1-v1_5".
Set the modulusLength attribute of algorithm to equal the modulusLength attribute of normalizedAlgorithm.
Set the publicExponent attribute of algorithm to equal the publicExponent attribute of normalizedAlgorithm.
Set the hash attribute of algorithm to equal the hash member of normalizedAlgorithm.
Let publicKey be a new CryptoKey representing the public key of the generated key pair.
Set the [[type]] internal slot of publicKey to "public"
Set the [[algorithm]] internal slot of publicKey to algorithm.
Set the [[extractable]] internal slot of publicKey to true.
Set the [[usages]] internal slot of publicKey to be the usage intersection of usages and [ "verify" ].
Let privateKey be a new CryptoKey representing the private key of the generated key pair.
Set the [[type]] internal slot of privateKey to "private"
Set the [[algorithm]] internal slot of privateKey to algorithm.
Set the [[extractable]] internal slot of privateKey to extractable.
Set the [[usages]] internal slot of privateKey to be the usage intersection of usages and [ "sign" ].
Let result be a new CryptoKeyPair dictionary.
Set the publicKey attribute of result to be publicKey.
Set the privateKey attribute of result to be privateKey.
Return result.

Let keyData be the key data to be imported.
If format is "spki":
1. If usages contains an entry which is not "verify", then throw a SyntaxError.
2. Let spki be the result of running the parse a subjectPublicKeyInfo algorithm over keyData.
3. If an error occurred while parsing, then throw a DataError.
4. If the algorithm object identifier field of the algorithm AlgorithmIdentifier field of spki is not equal to the rsaEncryption object identifier defined in [RFC3447], then throw a DataError.
5. Let publicKey be the result of performing the parse an ASN.1 structure algorithm, with data as the subjectPublicKeyInfo field of spki, structure as the RSAPublicKey structure specified in Section A.1.1 of [RFC3447], and exactData set to true.
6. If an error occurred while parsing, or it can be determined that publicKey is not a valid public key according to [RFC3447], then throw a DataError.
7. Let key be a new CryptoKey that represents the RSA public key identified by publicKey.
8. Set the [[type]] internal slot of key to "public"
If format is "pkcs8":
1. If usages contains an entry which is not "sign" then throw a SyntaxError.
2. Let privateKeyInfo be the result of running the parse a privateKeyInfo algorithm over keyData.
3. If an error occurred while parsing, then throw a DataError.
4. If the algorithm object identifier field of the privateKeyAlgorithm PrivateKeyAlgorithm field of privateKeyInfo is not equal to the rsaEncryption object identifier defined in [RFC3447], then throw a DataError.
5. Let rsaPrivateKey be the result of performing the parse an ASN.1 structure algorithm, with data as the privateKey field of privateKeyInfo, structure as the RSAPrivateKey structure specified in Section A.1.2 of [RFC3447], and exactData set to true.
6. If an error occurred while parsing, or if rsaPrivateKey is not a valid RSA private key according to [RFC3447], then throw a DataError.
7. Let key be a new CryptoKey that represents the RSA private key identified by rsaPrivateKey.
8. Set the [[type]] internal slot of key to "private"
If format is "jwk":
1. If keyData is a JsonWebKey dictionary:
  
  Let jwk equal keyData.
  
  Otherwise:
  
  Throw a DataError.
2. If the d field of jwk is present and usages contains an entry which is not "sign", or, if the d field of jwk is not present and usages contains an entry which is not "verify" then throw a SyntaxError.
3. If the kty field of jwk is not a case-sensitive string match to "RSA", then throw a DataError.
4. If usages is non-empty and the use field of jwk is present and is not a case-sensitive string match to "sig", then throw a DataError.
5. If the key_ops field of jwk is present, and is invalid according to the requirements of JSON Web Key [JWK] or does not contain all of the specified usages values, then throw a DataError.
6. If the ext field of jwk is present and has the value false and extractable is true, then throw a DataError.
7. Let hash be a be a string whose initial value is undefined.
8. If the alg field of jwk is not present:
  
  Let hash be undefined.
  
  If the alg field is equal to the string "RS1":
  
  Let hash be the string "SHA-1".
  
  If the alg field is equal to the string "RS256":
  
  Let hash be the string "SHA-256".
  
  If the alg field is equal to the string "RS384":
  
  Let hash be the string "SHA-384".
  
  If the alg field is equal to the string "RS512":
  
  Let hash be the string "SHA-512".
  
  Otherwise:
  
  Perform any key import steps defined by other applicable specifications, passing format, jwk and obtaining hash.
  
  If an error occurred or there are no applicable specifications, throw a DataError.
9. If hash is not undefined:
  
  Let normalizedHash be the result of normalize an algorithm with alg set to hash and op set to digest.
  
  If normalizedHash is not equal to the hash member of normalizedAlgorithm, throw a DataError.
10. If the d field of jwk is present:
  
  If jwk does not meet the requirements of Section 6.3.2 of JSON Web Algorithms [JWA], then throw a DataError.
  
  Let privateKey represents the RSA private key identified by interpreting jwk according to Section 6.3.2 of JSON Web Algorithms [JWA].
  
  If privateKey is not a valid RSA private key according to [RFC3447], then throw a DataError.
  
  Let key be a new CryptoKey object that represents privateKey.
  
  Set the [[type]] internal slot of key to "private"
  
  Otherwise:
  
  If jwk does not meet the requirements of Section 6.3.1 of JSON Web Algorithms [JWA], then throw a DataError.
  
  Let publicKey represent the RSA public key identified by interpreting jwk according to Section 6.3.1 of JSON Web Algorithms [JWA].
  
  If publicKey can be determined to not be a valid RSA public key according to [RFC3447], then throw a DataError.
  
  Let key be a new CryptoKey representing publicKey.
  
  Set the [[type]] internal slot of key to "public"
Otherwise:

throw a NotSupportedError.
Let algorithm be a new RsaHashedKeyAlgorithm dictionary.
Set the name attribute of algorithm to "RSASSA-PKCS1-v1_5"
Set the modulusLength attribute of algorithm to the length, in bits, of the RSA public modulus.
Set the publicExponent attribute of algorithm to the BigInteger representation of the RSA public exponent.
Set the hash attribute of algorithm to the hash member of normalizedAlgorithm.
Set the [[algorithm]] internal slot of key to algorithm.
Return key.

Let key be the key to be exported.
If the underlying cryptographic key material represented by the [[handle]] internal slot of key cannot be accessed, then throw an OperationError.
If format is "spki"
1. If the [[type]] internal slot of key is not "public", then throw an InvalidAccessError.
2. Let data be an instance of the SubjectPublicKeyInfo ASN.1 structure defined in [RFC5280] with the following properties:
  - Set the algorithm field to an AlgorithmIdentifier ASN.1 type with the following properties:
    
    Set the algorithm field to the OID rsaEncryption defined in [RFC3447].
    
    Set the params field to the ASN.1 type NULL.
  - Set the subjectPublicKey field to the result of DER-encoding an RSAPublicKey ASN.1 type, as defined in [RFC3447], Appendix A.1.1, that represents the RSA public key represented by the [[handle]] internal slot of key
3. Let result be the result of DER-encoding data.
If format is "pkcs8":
1. If the [[type]] internal slot of key is not "private", then throw an InvalidAccessError.
2. Let data be an instance of the PrivateKeyInfo ASN.1 structure defined in [RFC5208] with the following properties:
  - Set the version field to 0.
  - Set the privateKeyAlgorithm field to a PrivateKeyAlgorithmIdentifier ASN.1 type with the following properties:
    
    Set the algorithm field to the OID rsaEncryption defined in [RFC3447].
    
    Set the params field to the ASN.1 type NULL.
  - Set the privateKey field to the result of DER-encoding an RSAPrivateKey ASN.1 type, as defined in [RFC3447], Appendix A.1.2, that represents the RSA private key represented by the [[handle]] internal slot of key
    
    Note
    [RFC5208] specifies that the encoding of this field should be BER encoded in Section 5 (as a "for example"). However, to avoid requiring WebCrypto implementations support BER-encoding and BER-decoding, only DER encodings are produced or accepted.
3. Let result be the result of DER-encoding data.
If format is "jwk":
1. Let jwk be a new JsonWebKey dictionary.
2. Set the kty attribute of jwk to the string "RSA".
3. Let hash be the name attribute of the hash attribute of the [[algorithm]] internal slot of key.
4. If hash is "SHA-1":
  
  Set the alg attribute of jwk to the string "RS1".
  
  If hash is "SHA-256":
  
  Set the alg attribute of jwk to the string "RS256".
  
  If hash is "SHA-384":
  
  Set the alg attribute of jwk to the string "RS384".
  
  If hash is "SHA-512":
  
  Set the alg attribute of jwk to the string "RS512".
  
  Otherwise:
  
  Perform any

Algorithm name	encrypt	decrypt	sign	verify	digest	generateKey	deriveKey	deriveBits	importKey	exportKey	wrapKey	unwrapKey
RSASSA-PKCS1-v1_5			✔	✔		✔			✔	✔
RSA-PSS			✔	✔		✔			✔	✔
RSA-OAEP	✔	✔				✔			✔	✔	✔	✔
ECDSA			✔	✔		✔			✔	✔
ECDH						✔	✔	✔	✔	✔
Ed25519			✔	✔		✔			✔	✔
X25519						✔	✔	✔	✔	✔
AES-CTR	✔	✔				✔			✔	✔	✔	✔
AES-CBC	✔	✔				✔			✔	✔	✔	✔
AES-GCM	✔	✔				✔			✔	✔	✔	✔
AES-KW						✔			✔	✔	✔	✔
HMAC			✔	✔		✔			✔	✔
SHA-1					✔
SHA-256					✔
SHA-384					✔
SHA-512					✔
HKDF							✔	✔	✔
PBKDF2							✔	✔	✔

Web Cryptography Level 2

Abstract

Status of This Document

1. Introduction

2. Use Cases

2.1 Multi-factor Authentication

2.2 Protected Document Exchange

2.3 Cloud Storage

2.4 Document Signing

2.5 Data Integrity Protection

2.6 Secure Messaging

2.7 JavaScript Object Signing and Encryption (JOSE)

3. Conformance

3.1 Extensibility

4. Scope

4.1 Level of abstraction

4.2 Cryptographic algorithms

4.3 Out of scope

5. Concepts

5.1 Underlying Cryptographic Implementation

5.2 Key Storage

6. Security considerations

6.1 Security considerations for implementers

6.2 Security considerations for authors

6.3 Security considerations for users

7. Privacy considerations

8. Dependencies

9. Terminology

10. Crypto interface

10.1 Methods and Parameters

10.1.1 The getRandomValues method

10.1.2 The randomUUID method

10.2 Attributes

10.2.1 The subtle attribute

11. Algorithm dictionary

11.1 Algorithm Dictionary Members

12. KeyAlgorithm dictionary

12.1 Description

12.2 KeyAlgorithm dictionary members

13. CryptoKey interface

13.1 Description

13.2 Key interface data types

13.3 CryptoKey internal slots

13.4 CryptoKey interface members

13.5 Serialization and deserialization steps

14. SubtleCrypto interface

14.1 Data Types

14.2 Task Source

14.3 Methods and Parameters

14.3.1 The encrypt method

14.3.2 The decrypt method

14.3.3 The sign method

14.3.4 The verify method

14.3.5 The digest method

14.3.6 The generateKey method

14.3.7 The deriveKey method

14.3.8 The deriveBits method

14.3.9 The importKey method

14.3.10 The exportKey method

14.3.11 The wrapKey method

14.3.12 The unwrapKey method

14.4 Exceptions

15. JsonWebKey dictionary

16. BigInteger

17. CryptoKeyPair dictionary

18. Algorithms

18.1 Overview

18.2 Concepts

18.2.1 Naming

18.2.2 Supported Operations

18.2.3 Normalization

18.3 Specification Conventions

18.4 Algorithm Normalization

18.4.1 Description

18.4.2 Internal State Objects

18.4.3 Defining an Algorithm

18.4.4 Normalizing an algorithm

18.5 Recommendations

18.5.1 For Authors

18.5.2 For Implementers

11.1 `Algorithm` Dictionary Members

20.3 `RsaKeyGenParams` dictionary

20.4 `RsaHashedKeyGenParams` dictionary

20.5 `RsaKeyAlgorithm` dictionary

20.6 `RsaHashedKeyAlgorithm` dictionary

20.7 `RsaHashedImportParams` dictionary