dh-derivebits.js

/*
 * Arguments:
 *   priv: CryptoKey representing a DH private key
 *   pub: CryptoKey representing a DH public key
 *
 * Returns: Promise resolving to ArrayBuffer
 */
async function secret(priv, pub) {
  return await window.crypto.subtle.deriveBits(
    {
        name: "DH",
        //NOTE: THIS IS A SMALL PRIME FOR TESTING ONLY! DO NOT USE IT FOR REAL!
        //See http://datatracker.ietf.org/doc/rfc3526/ for better primes
        prime: new Uint8Array([
            255,255,255,255,255,255,255,255,201,15,218,162,33,104,194,52,196,198,98,139,
            128,220,28,209,41,2,78,8,138,103,204,116,2,11,190,166,59,19,155,34,81,74,8,
            121,142,52,4,221,239,149,25,179,205,58,67,27,48,43,10,109,242,95,20,55,79,225,
            53,109,109,81,194,69,228,133,181,118,98,94,126,198,244,76,66,233,166,55,237,
            107,11,255,92,182,244,6,183,237,238,56,107,251,90,137,159,165,174,159,36,17,
            124,75,31,230,73,40,102,81,236,228,91,61,194,0,124,184,161,99,191,5,152,218,
            72,54,28,85,211,154,105,22,63,168,253,36,207,95,131,101,93,35,220,163,173,
            150,28,98,243,86,32,133,82,187,158,213,41,7,112,150,150,109,103,12,53,78,74,
            188,152,4,241,116,108,8,202,35,115,39,255,255,255,255,255,255,255,255
        ]),
        generator: new Uint8Array([2]),
        public: pub
    },
    priv, //your DH private key from generateKey or importKey
    256//the number of bits you want to derive
    );
}