private void ECDH_GenerateEphemeral(EncryptMessage msg)
{
CBORObject epk = CBORObject.NewMap();
if (_mKey.AsString("kty") == "EC")
{
X9ECParameters p = NistNamedCurves.GetByName(_mKey.AsString("crv"));
ECDomainParameters parameters = new ECDomainParameters(p.Curve, p.G, p.N, p.H);
ECKeyPairGenerator pGen = new ECKeyPairGenerator();
ECKeyGenerationParameters genParam = new ECKeyGenerationParameters(parameters, Message.s_PRNG);
pGen.Init(genParam);
AsymmetricCipherKeyPair p1 = pGen.GenerateKeyPair();
epk.Add("kty", "EC");
epk.Add("crv", _mKey.AsString("crv"));
ECPublicKeyParameters priv = (ECPublicKeyParameters)p1.Public;
epk.Add("x", priv.Q.Normalize().XCoord.ToBigInteger().ToByteArrayUnsigned());
epk.Add("y", priv.Q.Normalize().YCoord.ToBigInteger().ToByteArrayUnsigned());
}
else if (_mKey.AsString("kty") == "OKP")
{
switch (_mKey.AsString("crv"))
{
case "X25519":
Ed25519KeyPairGenerator pGen = new Ed25519KeyPairGenerator();
Ed25519KeyGenerationParameters genParam = new Ed25519KeyGenerationParameters(Message.s_PRNG);
pGen.Init(genParam);
AsymmetricCipherKeyPair p1 = pGen.GenerateKeyPair();
Ed25519PublicKeyParameters pub = (Ed25519PublicKeyParameters)p1.Public;
epk.Add("kty", "OKP");
epk.Add("crv", "X25519");
epk.Add("x", pub.GetEncoded());
break;
default:
throw new JoseException("Unknown OPK curve");
}
}
else
{
throw new JoseException("Internal Error");
}
if (msg.FindAttribute(CBORObject.FromObject("epk"), PROTECTED) != null)
{
msg.AddAttribute(CBORObject.FromObject("epk"), epk, PROTECTED);
}
else if (msg.FindAttribute(CBORObject.FromObject("epk"), PROTECTED) != null)
{
msg.AddAttribute(CBORObject.FromObject("epk"), epk, PROTECTED);
}
else
{
AddAttribute("epk", epk, UNPROTECTED);
}
}
private void AES_GCM_KeyWrap(int keySize, EncryptMessage msg)
{
if (_mKey.AsString("kty") != "oct")
{
throw new JoseException("Incorrect key type");
}
byte[] keyBytes = _mKey.AsBytes("k");
if (keyBytes.Length != keySize / 8)
{
throw new JoseException("Key is not the correct size");
}
GcmBlockCipher cipher = new GcmBlockCipher(new AesEngine(), new BasicGcmMultiplier());
KeyParameter contentKey;
// The requirements from JWA
// IV is 96 bits
// Authentication tag is 128 bits
// key sizes are 128, 192 and 256 bits
// Keywrap says that there is no AAD
contentKey = new KeyParameter(keyBytes);
byte[] a = new byte[0];
byte[] iv = new byte[96 / 8];
Message.s_PRNG.NextBytes(iv);
if (msg.FindAttribute(CBORObject.FromObject("iv"), PROTECTED) != null)
{
msg.AddAttribute("iv", Message.base64urlencode(iv), PROTECTED);
}
else if (msg.FindAttribute(CBORObject.FromObject("iv"), UNPROTECTED) != null)
{
msg.AddAttribute("iv", Message.base64urlencode(iv), UNPROTECTED);
}
else
{
UnprotectedMap.Add("iv", Message.base64urlencode(iv));
}
AeadParameters parameters = new AeadParameters(contentKey, 128, iv, a);
cipher.Init(true, parameters);
byte[] c = new byte[cipher.GetOutputSize(_payload.Length)];
int len = cipher.ProcessBytes(_payload, 0, _payload.Length, c, 0);
len += cipher.DoFinal(c, len);
if (len != c.Length)
{
throw new JoseException("NYI");
}
byte[] tag = new byte[128 / 8];
Array.Copy(c, c.Length - tag.Length, tag, 0, tag.Length);
if (msg.FindAttribute(CBORObject.FromObject("tag"), PROTECTED) != null)
{
msg.AddAttribute("tag", Message.base64urlencode(tag), PROTECTED);
}
else if (msg.FindAttribute(CBORObject.FromObject("tag"), UNPROTECTED) != null)
{
msg.AddAttribute("tag", Message.base64urlencode(tag), UNPROTECTED);
}
else
{
UnprotectedMap.Add("tag", Message.base64urlencode(tag));
}
_rgbEncrypted = c;
Array.Resize(ref _rgbEncrypted, c.Length - tag.Length);
}