⚡fcrand (fast crypto rand)

fcrand is a high-performance drop-in replacement for Go's crypto/rand.<br>By Stan Drapkin.

Usage

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"

Features

• 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)

⚙️Before:

import (
    "crypto/rand"
)

✅ After:

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

Example

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)
}

Documentation

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

Requirements

• Go 1.24+

Installation

Using go get

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 Ready

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

Benchmarks

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.

Serial bench (1 goroutine):

| buf size | #g | fcrand ns/op | crypto/rand ns/op | speedup % | speedup x | |------|---|---------|---------|------|-------| | 0 | 1 | 3.08 | 134.90 | 98% | 43.8x | | 1 | 1 | 23.21 | 209.30 | 89% | 9x | | 2 | 1 | 20.74 | 186.80 | 89% | 9x | | 3 | 1 | 19.80 | 181.50 | 89% | 9.2x | | 4 | 1 | 18.80 | 178.40 | 89% | 9.5x | | 5 | 1 | 20.04 | 182.00 | 89% | 9.1x | | 6 | 1 | 20.35 | 180.20 | 89% | 8.9x | | 7 | 1 | 27.09 | 186.10 | 85% | 6.9x | | 8 | 1 | 29.66 | 184.30 | 84% | 6.2x | | 9 | 1 | 29.31 | 189.40 | 85% | 6.5x | | 12 | 1 | 31.36 | 230.30 | 86% | 7.3x | | 16 | 1 | 34.62 | 208.20 | 83% | 6x | | 17 | 1 | 39.44 | 200.90 | 80% | 5.1x | | 25 | 1 | 41.59 | 219.90 | 81% | 5.3x | | 31 | 1 | 44.47 | 226.20 | 80% | 5.1x | | 32 | 1 | 37.36 | 223.00 | 83% | 6x | | 33 | 1 | 41.45 | 231.10 | 82% | 5.6x | | 48 | 1 | 45.92 | 252.10 | 82% | 5.5x | | 56 | 1 | 49.69 | 270.70 | 82% | 5.4x | | 57 | 1 | 52.92 | 329.70 | 84% | 6.2x | | 64 | 1 | 53.59 | 300.50 | 82% | 5.6x | | 65 | 1 | 72.28 | 290.10 | 75% | 4x | | 128 | 1 | 83.68 | 373.60 | 78% | 4.5x | | 256 | 1 | 139.40 | 423.40 | 67% | 3x | | 512 | 1 | 253.30 | 502.50 | 50% | 2x | | 513 | 1 | 554.30 | 545.20 | -2% | 1x | | 1024 | 1 | 702.60 | 688.80 | -2% | 1x | | 2048 | 1 | 1049.00 | 1120.00 | 6% | 1.1x | | 4096 | 1 | 1784.00 | 1775.00 | -1% | 1x |

Concurrent bench (64 goroutines on a 16 vCPU machine):

| buf size | #g | fcrand ns/op | crypto/rand ns/op | speedup % | speedup x | |------|----|--------|--------|-----|-------| | 0 | 64 | 0.72 | 58.45 | 99% | 81.2x | | 1 | 64 | 6.48 | 72.86 | 91% | 11.2x | | 2 | 64 | 6.37 | 73.87 | 91% | 11.6x | | 3 | 64 | 11.37 | 76.99 | 85% | 6.8x | | 4 | 64 | 12.24 | 85.54 | 86% | 7x | | 5 | 64 | 11.70 | 82.37 | 86% | 7x | | 6 | 64 | 11.88 | 89.45 | 87% | 7.5x | | 7 | 64 | 12.51 | 84.41 | 85% | 6.7x | | 8 | 64 | 13.38 | 80.34 | 83% | 6x | | 9 | 64 | 14.95 | 81.98 | 82% | 5.5x | | 12 | 64 | 14.10 | 80.43 | 82% | 5.7x | | 16 | 64 | 15.42 | 84.61 | 82% | 5.5x | | 17 | 64 | 14.85 | 93.45 | 84% | 6.3x | | 25 | 64 | 17.71 | 97.25 | 82% | 5.5x | | 31 | 64 | 18.72 | 97.43 | 81% | 5.2x | | 32 | 64 | 14.61 | 98.35 | 85% | 6.7x | | 33 | 64 | 15.81 | 102.00 | 85% | 6.5x | | 48 | 64 | 17.11 | 111.80 | 85% | 6.5x | | 56 | 64 | 18.06 | 122.10 | 85% | 6.8x | | 57 | 64 | 18.51 | 122.20 | 85% | 6.6x | | 64 | 64 | 18.68 | 127.60 | 85% | 6.8x | | 65 | 64 | 20.27 | 126.30 | 84% | 6.2x | | 128 | 64 | 28.68 | 142.20 | 80% | 5x | | 256 | 64 | 55.05 | 156.60 | 65% | 2.8x | | 512 | 64 | 100.50 | 182.10 | 45% | 1.8x | | 513 | 64 | 200.30 | 194.10 | -3% | 1x | | 1024 | 64 | 241.50 | 232.30 | -4% | 1x | | 2048 | 64 | 349.20 | 361.60 | 3% | 1x | | 4096 | 64 | 675.50 | 684.20 | 1% | 1x |