/**
* Get the secret data that has been agreed on through Diffie-Hellman key agreement protocol. Note
* that in the two party protocol, if the peer keys are already known, no other data needs to be
* sent in order to agree on a secret. That is, a secured message may be sent without any
* mandatory round-trip overheads.
*
* <p>It is illegal to call this member function if the private key has not been set (or
* generated).
*
* @param peerPublicKey the peer's public key.
* @returns the secret, which is an unsigned big-endian integer the same size as the
* Diffie-Hellman modulus.
*/
SecretKey getAgreedSecret(BigInteger peerPublicValue) {
try {
KeyFactory kf = JsseJce.getKeyFactory("DiffieHellman");
DHPublicKeySpec spec = new DHPublicKeySpec(peerPublicValue, modulus, base);
PublicKey publicKey = kf.generatePublic(spec);
KeyAgreement ka = JsseJce.getKeyAgreement("DiffieHellman");
ka.init(privateKey);
ka.doPhase(publicKey, true);
return ka.generateSecret("TlsPremasterSecret");
} catch (GeneralSecurityException e) {
throw new RuntimeException("Could not generate secret", e);
}
}
static DHPublicKeySpec getDHPublicKeySpec(PublicKey key) {
if (key instanceof DHPublicKey) {
DHPublicKey dhKey = (DHPublicKey) key;
DHParameterSpec params = dhKey.getParams();
return new DHPublicKeySpec(dhKey.getY(), params.getP(), params.getG());
}
try {
KeyFactory factory = JsseJce.getKeyFactory("DH");
return (DHPublicKeySpec) factory.getKeySpec(key, DHPublicKeySpec.class);
} catch (Exception e) {
throw new RuntimeException(e);
}
}