1. Find "crypto/rand" imports in your Go code
2. Add a blank identifier _ in front: _ "crypto/rand"
3. Add rand "github.com/sdrapkin/fcrand"

• Up to 10x faster for random data requests ≤512 bytes
• Maintains all cryptographic security guarantees of crypto/rand
• 100% API compatible with crypto/rand – true drop-in replacement
• Thread-safe with zero configuration (same as crypto/rand)

import (
    "crypto/rand"
)

import (
    _ "crypto/rand"
    rand "github.com/sdrapkin/fcrand"
)

go playground

package main

import (
	"fmt"

	rand "github.com/sdrapkin/fcrand"
)

func main() {
	// Using rand.Read()
	buf := make([]byte, 16)
	rand.Read(buf)
	fmt.Printf("rand.Read buf:   [%x]\n", buf)

	// Using rand.Reader
	rand.Reader.Read(buf)
	fmt.Printf("rand.Reader buf: [%x]\n", buf)

	// Using .Text()
	token := rand.Text()
	fmt.Printf("token: [%s]\n", token)

	// Use .Prime() with rand.Reader
	key, err := rand.Prime(rand.Reader, 1024)
	fmt.Printf("prime: [%q]\n%v\n", key, err)
}

Full go doc style documentation: https://pkg.go.dev/github.com/sdrapkin/fcrand

• Go 1.24+

To install the fcrand package, run the following command:

go get -u github.com/sdrapkin/fcrand

To use the fcrand package in your Go project, import it as follows:

import rand "github.com/sdrapkin/fcrand"

• FIPS-140 ready (https://go.dev/doc/security/fips140)
  • set GODEBUG=fips140=on environment variable
  • https://go.dev/blog/fips140

Key observations: fcrand delivers 5-10x speedups for typical small requests, with even better concurrent performance. Performance falls back to crypto/rand levels at 512+ bytes as designed.