public SenderMessageKey(uint iteration, byte[] seed)
{
byte[] derivative = new HKDFv3().deriveSecrets(seed, Encoding.UTF8.GetBytes("WhisperGroup"), 48);
byte[][] parts = ByteUtil.split(derivative, 16, 32);
this.iteration = iteration;
this.seed = seed;
this.iv = parts[0];
this.cipherKey = parts[1];
}
public byte[] encrypt(ProvisionMessage message)// throws InvalidKeyException
{
ECKeyPair ourKeyPair = Curve.generateKeyPair();
byte[] sharedSecret = Curve.calculateAgreement(theirPublicKey, ourKeyPair.getPrivateKey());
byte[] derivedSecret = new HKDFv3().deriveSecrets(sharedSecret, Encoding.UTF8.GetBytes("TextSecure Provisioning Message"), 64);
byte[][] parts = Util.split(derivedSecret, 32, 32);
byte[] version = { 0x01 };
byte[] ciphertext = getCiphertext(parts[0], message.ToByteArray());
byte[] mac = getMac(parts[1], Util.join(version, ciphertext));
byte[] body = Util.join(version, ciphertext, mac);
return ProvisionEnvelope.CreateBuilder()
.SetPublicKey(ByteString.CopyFrom(ourKeyPair.getPublicKey().serialize()))
.SetBody(ByteString.CopyFrom(body))
.Build()
.ToByteArray();
}
