private byte[] EncryptSessionInfo(byte[] sessionInfo, SecureRandom random)
{
if (pubKey.Algorithm != PublicKeyAlgorithmTag.ECDH)
{
IBufferedCipher c;
switch (pubKey.Algorithm)
{
case PublicKeyAlgorithmTag.RsaEncrypt:
case PublicKeyAlgorithmTag.RsaGeneral:
c = CipherUtilities.GetCipher("RSA//PKCS1Padding");
break;
case PublicKeyAlgorithmTag.ElGamalEncrypt:
case PublicKeyAlgorithmTag.ElGamalGeneral:
c = CipherUtilities.GetCipher("ElGamal/ECB/PKCS1Padding");
break;
case PublicKeyAlgorithmTag.Dsa:
throw new PgpException("Can't use DSA for encryption.");
case PublicKeyAlgorithmTag.ECDsa:
throw new PgpException("Can't use ECDSA for encryption.");
default:
throw new PgpException("unknown asymmetric algorithm: " + pubKey.Algorithm);
}
AsymmetricKeyParameter akp = pubKey.GetKey();
c.Init(true, new ParametersWithRandom(akp, random));
return(c.DoFinal(sessionInfo));
}
ECDHPublicBcpgKey ecKey = (ECDHPublicBcpgKey)pubKey.PublicKeyPacket.Key;
// Generate the ephemeral key pair
IAsymmetricCipherKeyPairGenerator gen = GeneratorUtilities.GetKeyPairGenerator("ECDH");
gen.Init(new ECKeyGenerationParameters(ecKey.CurveOid, random));
AsymmetricCipherKeyPair ephKp = gen.GenerateKeyPair();
ECPrivateKeyParameters ephPriv = (ECPrivateKeyParameters)ephKp.Private;
ECPublicKeyParameters ephPub = (ECPublicKeyParameters)ephKp.Public;
ECPublicKeyParameters pub = (ECPublicKeyParameters)pubKey.GetKey();
ECPoint S = pub.Q.Multiply(ephPriv.D).Normalize();
KeyParameter key = new KeyParameter(Rfc6637Utilities.CreateKey(pubKey.PublicKeyPacket, S));
IWrapper w = PgpUtilities.CreateWrapper(ecKey.SymmetricKeyAlgorithm);
w.Init(true, new ParametersWithRandom(key, random));
byte[] paddedSessionData = PgpPad.PadSessionData(sessionInfo);
byte[] C = w.Wrap(paddedSessionData, 0, paddedSessionData.Length);
byte[] VB = new MPInteger(new BigInteger(1, ephPub.Q.GetEncoded(false))).GetEncoded();
byte[] rv = new byte[VB.Length + 1 + C.Length];
Array.Copy(VB, 0, rv, 0, VB.Length);
rv[VB.Length] = (byte)C.Length;
Array.Copy(C, 0, rv, VB.Length + 1, C.Length);
return(rv);
}
private byte[] RecoverSessionData(PgpPrivateKey privKey)
{
byte[][] secKeyData = keyData.GetEncSessionKey();
if (keyData.Algorithm == PublicKeyAlgorithmTag.ECDH)
{
ECDHPublicBcpgKey ecKey = (ECDHPublicBcpgKey)privKey.PublicKeyPacket.Key;
X9ECParameters x9Params = ECKeyPairGenerator.FindECCurveByOid(ecKey.CurveOid);
byte[] enc = secKeyData[0];
int pLen = ((((enc[0] & 0xff) << 8) + (enc[1] & 0xff)) + 7) / 8;
byte[] pEnc = new byte[pLen];
Array.Copy(enc, 2, pEnc, 0, pLen);
byte[] keyEnc = new byte[enc[pLen + 2]];
Array.Copy(enc, 2 + pLen + 1, keyEnc, 0, keyEnc.Length);
ECPoint publicPoint = x9Params.Curve.DecodePoint(pEnc);
ECPrivateKeyParameters privKeyParams = (ECPrivateKeyParameters)privKey.Key;
ECPoint S = publicPoint.Multiply(privKeyParams.D).Normalize();
KeyParameter key = new KeyParameter(Rfc6637Utilities.CreateKey(privKey.PublicKeyPacket, S));
IWrapper w = PgpUtilities.CreateWrapper(ecKey.SymmetricKeyAlgorithm);
w.Init(false, key);
return(PgpPad.UnpadSessionData(w.Unwrap(keyEnc, 0, keyEnc.Length)));
}
IBufferedCipher cipher = GetKeyCipher(keyData.Algorithm);
try
{
cipher.Init(false, privKey.Key);
}
catch (InvalidKeyException e)
{
throw new PgpException("error setting asymmetric cipher", e);
}
if (keyData.Algorithm == PublicKeyAlgorithmTag.RsaEncrypt ||
keyData.Algorithm == PublicKeyAlgorithmTag.RsaGeneral)
{
byte[] bi = secKeyData[0];
cipher.ProcessBytes(bi, 2, bi.Length - 2);
}
else
{
ElGamalPrivateKeyParameters k = (ElGamalPrivateKeyParameters)privKey.Key;
int size = (k.Parameters.P.BitLength + 7) / 8;
ProcessEncodedMpi(cipher, size, secKeyData[0]);
ProcessEncodedMpi(cipher, size, secKeyData[1]);
}
try
{
return(cipher.DoFinal());
}
catch (Exception e)
{
throw new PgpException("exception decrypting secret key", e);
}
}
