return new SecretKeySpec(derivedKey, cekAlg);
}
private byte[] kdf(ContentEncryptionKeyDescriptor cekDesc, Headers headers, byte[] z)
{
KdfUtil kdf = new KdfUtil();
int keydatalen = ByteUtil.bitLength(cekDesc.getContentEncryptionKeyByteLength());
/*
AlgorithmID In the Direct Key Agreement case, this is set to the
octets of the UTF-8 representation of the "enc" header parameter
value. In the Key Agreement with Key Wrapping case, this is set
to the octets of the UTF-8 representation of the "alg" header
parameter value.*/
String algorithmID = headers.getStringHeaderValue(algorithmIdHeaderName);
String partyUInfo = headers.getStringHeaderValue(HeaderParameterNames.AGREEMENT_PARTY_U_INFO);
String partyVInfo = headers.getStringHeaderValue(HeaderParameterNames.AGREEMENT_PARTY_V_INFO);
return kdf.kdf(z, keydatalen, algorithmID, partyUInfo, partyVInfo);
}