example using node.js crypto API with aes-256-gcm

crypto-aes-256-gcm-demo.js

const buffer = require('buffer');
const crypto = require('crypto');

// Demo implementation of using `aes-256-gcm` with node.js's `crypto` lib.
const aes256gcm = (key) => {
  const ALGO = 'aes-256-gcm';

  // encrypt returns base64-encoded ciphertext
  const encrypt = (str) => {
    // The `iv` for a given key must be globally unique to prevent
    // against forgery attacks. `randomBytes` is convenient for
    // demonstration but a poor way to achieve this in practice.
    //
    // See: e.g. https://csrc.nist.gov/publications/detail/sp/800-38d/final
    const iv = new Buffer(crypto.randomBytes(12), 'utf8');
    const cipher = crypto.createCipheriv(ALGO, key, iv);

    // Hint: Larger inputs (it's GCM, after all!) should use the stream API
    let enc = cipher.update(str, 'utf8', 'base64');
    enc += cipher.final('base64');
    return [enc, iv, cipher.getAuthTag()];
  };

  // decrypt decodes base64-encoded ciphertext into a utf8-encoded string
  const decrypt = (enc, iv, authTag) => {
    const decipher = crypto.createDecipheriv(ALGO, key, iv);
    decipher.setAuthTag(authTag);
    let str = decipher.update(enc, 'base64', 'utf8');
    str += decipher.final('utf8');
    return str;
  };

  return {
    encrypt,
    decrypt,
  };
};

const KEY = new Buffer(crypto.randomBytes(32), 'utf8');

const aesCipher = aes256gcm(KEY);

const [encrypted, iv, authTag] = aesCipher.encrypt('hello, world');
const decrypted = aesCipher.decrypt(encrypted, iv, authTag);

console.log(decrypted); // 'hello, world'

I agree with your points @coryhardman , GCM is not a method that can blindly be thrown into a project. Yes, it is quite a secure one, but it is a "double-edged sword" per se. Only with a well-implemented key and IV generation process, it shines.

Reading the above, i'm wondering how to send the encrypted message over the internet?
Is it save to send all 3 of values or do we need to send the tag an other way?

Reading the above, i'm wondering how to send the encrypted message over the internet? Is it save to send all 3 of values or do we need to send the tag an other way?

@nielsnl68 Did you find any better option for this? to send this over the internet?

I did not implemented it, and stick to the CBC variant for now. Also, I'm not an expert and don't dear to advice anything.

Most applications should consider using the new KeyObject API instead of passing keys as strings or 
Buffers due to improved security features. -https://nodejs.org/api/crypto.html#class-keyobject

e.g. generateKey('aes', { length: 256 }