How to create a pair private/public keys using Node.js crypto?

I have to generate two keys (private and public) to encrypt a text with the public and let the user with the private key decrypt the text.

Is it possible with the module Crypto?

nodejs v10.12 now supports this natively with crypto.generateKeyPair

const { generateKeyPair } = require('crypto');
generateKeyPair('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
    cipher: 'aes-256-cbc',
    passphrase: 'top secret'
  }
}, (err, publicKey, privateKey) => {
  // Handle errors and use the generated key pair.
});

Use the crypto module from npm to generate KeyPair.

var crypto = require('crypto');

var prime_length = 60;
var diffHell = crypto.createDiffieHellman(prime_length);

diffHell.generateKeys('base64');
console.log("Public Key : " ,diffHell.getPublicKey('base64'));
console.log("Private Key : " ,diffHell.getPrivateKey('base64'));

console.log("Public Key : " ,diffHell.getPublicKey('hex'));
console.log("Private Key : " ,diffHell.getPrivateKey('hex'));

Above is a example snippet. To know more checkout documentation http://nodejs.org/api/crypto.html

The following code works, but I'm not a professional cryptographer, so some comments here would be useful.

I've used the ursa RSA module, instead of crypto.

I am concerned that if similar data were encrypted directly, without a pass of AES or similar, then it might be trivial to break this. Comments please...

var ursa = require('ursa');
var fs = require('fs');

// create a pair of keys (a private key contains both keys...)
var keys = ursa.generatePrivateKey();
console.log('keys:', keys);

// reconstitute the private key from a base64 encoding
var privPem = keys.toPrivatePem('base64');
console.log('privPem:', privPem);

var priv = ursa.createPrivateKey(privPem, '', 'base64');

// make a public key, to be used for encryption
var pubPem = keys.toPublicPem('base64');
console.log('pubPem:', pubPem);

var pub = ursa.createPublicKey(pubPem, 'base64');

// encrypt, with the public key, then decrypt with the private
var data = new Buffer('hello world');
console.log('data:', data);

var enc = pub.encrypt(data);
console.log('enc:', enc);

var unenc = priv.decrypt(enc);
console.log('unenc:', unenc);

After some further investigation http://en.wikipedia.org/w/index.php?title=RSA_%28cryptosystem%29&section=12#Attacks_against_plain_RSA it looks like ursa already does padding.

If you know how to get what you want from OpenSSL, I think it's perfectly reasonable to run OpenSSL using Node's child_process.

var cp = require('child_process')
  , assert = require('assert')
  ;

var privateKey, publicKey;
publicKey = '';
cp.exec('openssl genrsa 2048', function(err, stdout, stderr) {
  assert.ok(!err);
  privateKey = stdout;
  console.log(privateKey);
  makepub = cp.spawn('openssl', ['rsa', '-pubout']);
  makepub.on('exit', function(code) {
    assert.equal(code, 0); 
    console.log(publicKey);
  });
  makepub.stdout.on('data', function(data) {
    publicKey += data;
  });
  makepub.stdout.setEncoding('ascii');
  makepub.stdin.write(privateKey);
  makepub.stdin.end();  
});

const crypto = require('crypto');

  const { privateKey, publicKey } = crypto.generateKeyPairSync('rsa', {
    modulusLength: 2048,
    publicKeyEncoding: {
      type: 'spki',
      format: 'pem'
    },
    privateKeyEncoding: {
      type: 'pkcs8',
      format: 'pem'
    }
  });