protected virtual TlsMac CreateTlsMac(IDigest digest, byte[] buf, ref int off)
{
int len = digest.GetDigestSize();
TlsMac mac = new TlsMac(digest, buf, off, len);
off += len;
return(mac);
}
public TlsBlockCipher(TlsClientContext context, IBlockCipher encryptCipher,
IBlockCipher decryptCipher, IDigest writeDigest, IDigest readDigest, int cipherKeySize)
{
this.context = context;
this.encryptCipher = encryptCipher;
this.decryptCipher = decryptCipher;
int prfSize = (2 * cipherKeySize) + writeDigest.GetDigestSize()
+ readDigest.GetDigestSize() + encryptCipher.GetBlockSize()
+ decryptCipher.GetBlockSize();
SecurityParameters securityParameters = context.SecurityParameters;
byte[] keyBlock = TlsUtilities.PRF(securityParameters.masterSecret, "key expansion",
TlsUtilities.Concat(securityParameters.serverRandom, securityParameters.clientRandom),
prfSize);
int offset = 0;
// Init MACs
writeMac = CreateTlsMac(writeDigest, keyBlock, ref offset);
readMac = CreateTlsMac(readDigest, keyBlock, ref offset);
// Build keys
KeyParameter encryptKey = CreateKeyParameter(keyBlock, ref offset, cipherKeySize);
KeyParameter decryptKey = CreateKeyParameter(keyBlock, ref offset, cipherKeySize);
// Add IVs
ParametersWithIV encryptParams = CreateParametersWithIV(encryptKey,
keyBlock, ref offset, encryptCipher.GetBlockSize());
ParametersWithIV decryptParams = CreateParametersWithIV(decryptKey,
keyBlock, ref offset, decryptCipher.GetBlockSize());
if (offset != prfSize)
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
// Init Ciphers
encryptCipher.Init(true, encryptParams);
decryptCipher.Init(false, decryptParams);
}