code: function buildEcdhParam(public_algo, oid, cipher_algo, hash_algo, fingerprint) {
    const kdf_params = new type_kdf_params([hash_algo, cipher_algo]);
    return util.concatUint8Array([
      oid.write(),
      new Uint8Array([public_algo]),
      kdf_params.write(),
      util.str_to_Uint8Array("Anonymous Sender    "),
      fingerprint.subarray(0, 20)
    ]);
  }
docs: Build Param for ECDH algorithm (RFC 6637)