code: function(data, key, keysize) {
        var input, mode;
        if (keysize == null) {
          keysize = 512;
        }
        data = this.toHex(data);
        key = this.toHex(key);
        mode = "SHA-" + keysize;
        input = new jsSHA(data, "HEX");
        return input.getHMAC(key, "HEX", mode, "HEX");
      }
docs: Cryptographically hash data using HMAC.
  @param {String|Buffer} data The data to be hashed.
  @param {String|Buffer} key The key to use with HMAC.
  @param {Number} [keysize=512] The keysize for the hash function.
  @return {String} The hmac digest encoded as hex.