scrypt

Documentation

Overview

Package scrypt implements the scrypt key derivation function as defined in Colin Percival's paper "Stronger Key Derivation via Sequential Memory-Hard Functions" (https://www.tarsnap.com/scrypt/scrypt.pdf).

Example

package main

import (
	"encoding/base64"
	"fmt"
	"log"

	"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/crypto/scrypt"
)

func main() {
	// DO NOT use this salt value; generate your own random salt. 8 bytes is
	// a good length.
	salt := []byte{0xc8, 0x28, 0xf2, 0x58, 0xa7, 0x6a, 0xad, 0x7b}

	dk, err := scrypt.Key([]byte("some password"), salt, 1<<15, 8, 1, 32)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(base64.StdEncoding.EncodeToString(dk))
}

Output:

lGnMz8io0AUkfzn6Pls1qX20Vs7PGN6sbYQ2TQgY12M=

Index

• func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error)

Examples

• Package

Functions

func Key

func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error)

Key derives a key from the password, salt, and cost parameters, returning a byte slice of length keyLen that can be used as cryptographic key.

N is a CPU/memory cost parameter, which must be a power of two greater than 1. r and p must satisfy r * p < 2³⁰. If the parameters do not satisfy the limits, the function returns a nil byte slice and an error.

For example, you can get a derived key for e.g. AES-256 (which needs a 32-byte key) by doing:

dk, err := scrypt.Key([]byte("some password"), salt, 32768, 8, 1, 32)

The recommended parameters for interactive logins as of 2017 are N=32768, r=8 and p=1. The parameters N, r, and p should be increased as memory latency and CPU parallelism increases; consider setting N to the highest power of 2 you can derive within 100 milliseconds. Remember to get a good random salt.