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Encryption, Decryption

Encryption and Decryption of contents using crypto module

Example code:

index.js file

var inp_password = process.argv.slice(2)[0];
if (inp_password == undefined || inp_password.length < 6)
{
    console.log('Invalid password, it must be greater than 5 letters with no white space');
    console.log('Restart program and try again');
    process.exit(1);
}

var makepassword32bytes = require('./modules/makepassword32bytes.js');
var _32bytePassword = makepassword32bytes(inp_password);

var encdec = require('./modules/encdec.js');

var encMessage = encdec.encrypt('Hello world', _32bytePassword);

var decMessage = encdec.decrypt(encMessage, _32bytePassword);

console.log('Encrypted Message ', encMessage);
console.log('Decrypted Message ', decMessage);

encdec.js file

var crypto = require('crypto');

var IV_LENGTH = 16;

function encrypt(text, key) {

  var iv = crypto.randomBytes(IV_LENGTH);
  var cipher = crypto.createCipheriv('aes-256-cbc', new Buffer(key), iv);
  var encrypted = cipher.update(text);

  encrypted = Buffer.concat([encrypted, cipher.final()]);

  return iv.toString('hex') + ':' + encrypted.toString('hex');
}

function decrypt(text, key) {
  var textParts = text.split(':');
  var iv = new Buffer(textParts.shift(), 'hex');
  var encryptedText = new Buffer(textParts.join(':'), 'hex');
  var decipher = crypto.createDecipheriv('aes-256-cbc', new Buffer(key), iv);
  var decrypted = decipher.update(encryptedText);

  decrypted = Buffer.concat([decrypted, decipher.final()]);

  return decrypted.toString();
}


module.exports = { decrypt, encrypt };

makepassword32bytes.js file

var makepassword32bytes = function (text) {

    var data = text;
    while (data.length <= 32)
    {
        data += data;
    }
    data = data.substr(0, 32);
    return data;
}

module.exports = makepassword32bytes;

To ensure the encrypted content never produces the same output, we will use an Initialization Vector (IV) to add some randomness to the encryption algorithm. For this to be strong, we need to generate a unique random IV per encryption run – not a single fixed pre-defined IV. This is similar to a salt for password hashing, and will be stored with our encrypted data so we can decrypt it later along with the key.

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