public byte[] EncryptSessionInfo(ReadOnlySpan <byte> sessionInfo)
{
var publicKeyParams = ecdh.PublicKey.ExportParameters();
// Generate the ephemeral key pair
var ephemeralEcDh = CreateECDiffieHellman(publicKeyParams.Curve);
var derivedKey = ephemeralEcDh.DeriveKeyFromHash(
ecdh.PublicKey,
PgpUtilities.GetHashAlgorithmName(this.hashAlgorithm),
new byte[] { 0, 0, 0, 1 },
CreateUserKeyingMaterial(publicKeyParams.Curve.Oid));
derivedKey = derivedKey.AsSpan(0, PgpUtilities.GetKeySize(symmetricAlgorithm) / 8).ToArray();
byte[] paddedSessionData = PadSessionData(sessionInfo);
byte[] C = SymmetricKeyWrap.AESKeyWrapEncrypt(derivedKey, paddedSessionData);
var ep = ephemeralEcDh.PublicKey.ExportParameters();
byte[] VB = EncodePoint(ep.Q, publicKeyParams.Curve.Oid);
byte[] rv = new byte[VB.Length + 2 + 1 + C.Length];
MPInteger.TryWriteInteger(VB, rv, out _);
//Array.Copy(VB, 0, rv, 0, VB.Length);
rv[VB.Length + 2] = (byte)C.Length;
Array.Copy(C, 0, rv, VB.Length + 3, C.Length);
return(rv);
}
public bool TryDecryptSessionInfo(ReadOnlySpan <byte> encryptedSessionData, Span <byte> sessionData, out int bytesWritten)
{
var pEnc = MPInteger.ReadInteger(encryptedSessionData, out int pointBytesRead);
encryptedSessionData = encryptedSessionData.Slice(pointBytesRead);
int keyLen = encryptedSessionData[0];
var keyEnc = encryptedSessionData.Slice(1, keyLen);
var publicParams = ecdh.PublicKey.ExportParameters();
var publicPoint = DecodePoint(pEnc);
var otherEcdh = CreateECDiffieHellman(new ECParameters {
Curve = publicParams.Curve, Q = publicPoint
});
var derivedKey = ecdh.DeriveKeyFromHash(
otherEcdh.PublicKey,
PgpUtilities.GetHashAlgorithmName(this.hashAlgorithm),
new byte[] { 0, 0, 0, 1 },
CreateUserKeyingMaterial(publicParams.Curve.Oid));
derivedKey = derivedKey.AsSpan(0, PgpUtilities.GetKeySize(this.symmetricAlgorithm) / 8).ToArray();
var C = SymmetricKeyWrap.AESKeyWrapDecrypt(derivedKey, keyEnc.ToArray());
var data = UnpadSessionData(C);
if (sessionData.Length >= data.Length)
{
data.CopyTo(sessionData);
bytesWritten = data.Length;
return(true);
}
bytesWritten = 0;
return(false);
}
