private static void ReadGenericBlob(BinaryReader reader, int expectedSize, ECParameters dest, bool includePrivateParameters)
{
/* struct BCRYPT_ECCFULLKEY_BLOB
* {
* ULONG dwMagic; // BCRYPT_ECDSA_PUBLIC_GENERIC_MAGIC or BCRYPT_ECDSA_PRIVATE_GENERIC_MAGIC
* BCRYPT_ECC_PARAMETER_HEADER curveParameters;
* BYTE Qx[cbFieldLength] // X-coordinate of the public point.
* BYTE Qy[cbFieldLength] // Y-coordinate of the public point.
* BYTE d[cbSubgroupOrder] // Private key. Zero if only public key is required.
* }
*/
// The magic was read before.
var curve = new BCRYPT_ECC_PARAMETER_HEADER();
curve.ReadFrom(reader);
if (!curve.Equals(Secp256k1))
{
throw new NotSupportedException($"Unsupported curve: {curve}");
}
dest.Curve = JsonWebKeyCurveName.P256K;
var cbFieldLength = curve.Prime.Length;
dest.X = ValidateSize(reader.ReadBytes(cbFieldLength), expectedSize, nameof(dest.X));
dest.Y = ValidateSize(reader.ReadBytes(cbFieldLength), expectedSize, nameof(dest.Y));
if (includePrivateParameters)
{
dest.D = ValidateSize(reader.ReadBytes(cbFieldLength), expectedSize, nameof(dest.D));
}
}
private ECDsaCng ToGenericCurveEcdsa(int dwMagic, BCRYPT_ECC_PARAMETER_HEADER curveParameters, bool includePrivateParameters)
{
var sizeInBytes = curveParameters.KeySizeInBytes;
var keyBlob = new byte[curveParameters.KeyBlobSize];
using (var writer = new BinaryWriter(new MemoryStream(keyBlob)))
{
writer.Write(dwMagic);
curveParameters.WriteTo(writer);
AlignAndWrite(writer, X, sizeInBytes, nameof(X));
AlignAndWrite(writer, Y, sizeInBytes, nameof(Y));
if (includePrivateParameters)
{
AlignAndWrite(writer, D, sizeInBytes, nameof(D));
}
}
var key = CngKey.Import(keyBlob, includePrivateParameters ? CngKeyBlobFormat_EccFullPrivateBlob : CngKeyBlobFormat_EccFullPublicBlob);
return(new ECDsaCng(key));
}
