v/vlib/crypto/README.md

Description:

crypto is a module that exposes cryptographic algorithms to V programs.

Each submodule implements things differently, so be sure to consider the documentation of the specific algorithm you need, but in general, the method is to create a cipher struct using one of the module functions, and then to call the encrypt or decrypt method on that struct to actually encrypt or decrypt your data.

This module is a work-in-progress. For example, the AES implementation currently requires you to create a destination buffer of the correct size to receive the decrypted data, and the AesCipher encrypt and decrypt functions only operate on the first block of the src.

The implementations here are loosely based on Go's crypto package.

Examples:

AES:

import crypto.aes
import crypto.rand

fn main() {
	// remember to save this key somewhere if you ever want to decrypt your data
	key := rand.bytes(32)!
	println('KEY: ${key}')

	// this data is one block (16 bytes) big
	mut data := 'THIS IS THE DATA'.bytes()

	println('generating cipher')
	cipher := aes.new_cipher(key)

	println('performing encryption')
	mut encrypted := []u8{len: aes.block_size}
	cipher.encrypt(mut encrypted, data)
	println(encrypted)

	println('performing decryption')
	mut decrypted := []u8{len: aes.block_size}
	cipher.decrypt(mut decrypted, encrypted)
	println(decrypted)

	assert decrypted == data
}

JWT:

import crypto.hmac
import crypto.sha256
import encoding.base64
import json
import time

struct JwtHeader {
	alg string
	typ string
}

struct JwtPayload {
	sub  string
	name string
	iat  int
}

fn main() {
	sw := time.new_stopwatch()
	secret := 'your-256-bit-secret'
	token := make_token(secret)
	ok := auth_verify(secret, token)
	dt := sw.elapsed().microseconds()
	println('token: ${token}')
	println('auth_verify(secret, token): ${ok}')
	println('Elapsed time: ${dt} uS')
}

fn make_token(secret string) string {
	header := base64.url_encode(json.encode(JwtHeader{'HS256', 'JWT'}).bytes())
	payload := base64.url_encode(json.encode(JwtPayload{'1234567890', 'John Doe', 1516239022}).bytes())
	signature := base64.url_encode(hmac.new(secret.bytes(), '${header}.${payload}'.bytes(),
		sha256.sum, sha256.block_size))
	jwt := '${header}.${payload}.${signature}'
	return jwt
}

fn auth_verify(secret string, token string) bool {
	token_split := token.split('.')
	signature_mirror := hmac.new(secret.bytes(), '${token_split[0]}.${token_split[1]}'.bytes(),
		sha256.sum, sha256.block_size)
	signature_from_token := base64.url_decode(token_split[2])
	return hmac.equal(signature_from_token, signature_mirror)
}