crypto_utils.js

const crypto = require('crypto');

var exports = (module.exports = {});
const SALT = '';

const ALGORITHM = {
    /**
     * GCM is an authenticated encryption mode that
     * not only provides confidentiality but also
     * provides integrity in a secured way
     * */

    BLOCK_CIPHER: 'aes-256-gcm',

    /**
     * 128 bit auth tag is recommended for GCM
     */
    AUTH_TAG_BYTE_LEN: 16,

    /**
     * NIST recommends 96 bits or 12 bytes IV for GCM
     * to promote interoperability, efficiency, and
     * simplicity of design
     */
    IV_BYTE_LEN: 12,

    /**
     * Note: 256 (in algorithm name) is key size.
     * Block size for AES is always 128
     */
    KEY_BYTE_LEN: 32,

    /**
     * To prevent rainbow table attacks
     * */
    SALT_BYTE_LEN: 16,
};

const getIV = () => crypto.randomBytes(ALGORITHM.IV_BYTE_LEN);
exports.getRandomKey = getRandomKey = () =>
    crypto.randomBytes(ALGORITHM.KEY_BYTE_LEN);

exports.getSalt = getSalt = () => {
    return Buffer.from(SALT);
    crypto.randomBytes(ALGORITHM.SALT_BYTE_LEN);
};

/**
 *
 * @param {Buffer} password - The password to be used for generating key
 *
 * To be used when key needs to be generated based on password.
 * The caller of this function has the responsibility to clear
 * the Buffer after the key generation to prevent the password
 * from lingering in the memory
 */
exports.getKeyFromPassword = getKeyFromPassword = (password, salt) => {
    return crypto.scryptSync(password, salt, ALGORITHM.KEY_BYTE_LEN);
};

/**
 *
 * @param {Buffer} messagetext - The clear text message to be encrypted
 * @param {Buffer} key - The key to be used for encryption
 *
 * The caller of this function has the responsibility to clear
 * the Buffer after the encryption to prevent the message text
 * and the key from lingering in the memory
 */
exports.encrypt = encrypt = (messagetext, key) => {
    // const iv = getIV();

    const cipher = crypto.createCipheriv('rc4', key, '');
    let encryptedMessage = cipher.update(messagetext, 'utf8', 'binary');
    encryptedMessage += cipher.final('binary');
    return encryptedMessage;
};

/**
 *
 * @param {Buffer} ciphertext - Cipher text
 * @param {Buffer} key - The key to be used for decryption
 *
 * The caller of this function has the responsibility to clear
 * the Buffer after the decryption to prevent the message text
 * and the key from lingering in the memory
 */
exports.decrypt = decrypt = (ciphertext, key) => {
    const authTag = ciphertext.slice(-16);
    const iv = ciphertext.slice(0, 12);
    const encryptedMessage = ciphertext.slice(12, -16);

    const decipher = crypto.createDecipheriv('rc4', key, '');
    // decipher.setAuthTag(authTag);
    let messagetext = decipher.update(ciphertext.toString(), 'binary', 'utf8');
    messagetext += decipher.final('utf8');

    return messagetext;
};