example of encrypted pgp-style message sending involving two recipients

message.js

// handle signed numbers
var toHex = function(decimalInt) {
  if (decimalInt < 0) {
    decimalInt += 0xFFFFFFFF + 1;
  }

  return decimalInt.toString(16).toUpperCase();
};

var set1, set2, set3, pair1, pair2, sym_key='';
var msg = 'Super-secret message! Tell no one!';
var pass1 = 'password1'
  , pass2 = 'password2';


while (typeof set1 === 'undefined') {
  set1 = sjcl.ecc.ecdsa.generateKeys();
}

while (typeof set2 === 'undefined') {
  set2 = sjcl.ecc.ecdsa.generateKeys();
}

while (typeof set3 === 'undefined') {
  set3 = sjcl.ecc.ecdsa.generateKeys();
}

// create hex-based representation of symmetric key
sym_key = _.reduce(set3.sec.get(), function (sum, key) { return sum + toHex(key); }, '');

var emsg = sjcl.encrypt(sym_key, msg);
var rec1 = sjcl.encrypt(pass1, sym_key);
var rec2 = sjcl.encrypt(pass2, sym_key);

console.log('symmetric key: ' + sym_key);
console.log('encrypted message: ' + emsg);
console.log('encrypted symmetric key with pass1: ' + rec1);
console.log('encrypted symmetric key with pass2: ' + rec2);

// Now, store emsg, rec1, rec2 on the server, then...
var dec_sym_key = sjcl.decrypt(pass1, rec1);

var msg1 = sjcl.decrypt(dec_sym_key, emsg);
var msg2 = sjcl.decrypt(dec_sym_key, emsg);

console.log('original message: ' + msg);
console.log('decrypted message1: ' + msg1);
console.log('decrypted message2: ' + msg2);

Requires sjcl library and lodash / underscore. In prod, you would encrypt pair1 and pair2 with pass1 and pass2 respectively. Then back this up and use pair1 / pair2 private key for decryption.