internal static unsafe byte[] GetPrimeCurveParameterBlob(ref ECCurve curve)
{
// We need to build a key blob structured as follows:
// BCRYPT_ECC_PARAMETER_HEADER header
// byte[cbFieldLength] P
// byte[cbFieldLength] A
// byte[cbFieldLength] B
// byte[cbFieldLength] G.X
// byte[cbFieldLength] G.Y
// byte[cbSubgroupOrder] Order (n)
// byte[cbCofactor] Cofactor (h)
// byte[cbSeed] Seed
int blobSize = sizeof(BCRYPT_ECC_PARAMETER_HEADER) +
curve.Prime !.Length +
curve.A !.Length +
curve.B !.Length +
curve.G.X !.Length +
curve.G.Y !.Length +
curve.Order !.Length +
curve.Cofactor !.Length +
(curve.Seed == null ? 0 : curve.Seed.Length);
byte[] blob = new byte[blobSize];
fixed(byte *pBlob = &blob[0])
{
// Build the header
BCRYPT_ECC_PARAMETER_HEADER *pBcryptBlob = (BCRYPT_ECC_PARAMETER_HEADER *)pBlob;
pBcryptBlob->Version = Interop.BCrypt.BCRYPT_ECC_PARAMETER_HEADER_V1;
pBcryptBlob->cbCofactor = curve.Cofactor.Length;
pBcryptBlob->cbFieldLength = curve.A.Length; // P, A, B, X, Y have the same length
pBcryptBlob->cbSeed = curve.Seed == null ? 0 : curve.Seed.Length;
pBcryptBlob->cbSubgroupOrder = curve.Order.Length;
pBcryptBlob->CurveGenerationAlgId = ECCng.GetHashAlgorithmId(curve.Hash);
pBcryptBlob->CurveType = ECCng.ConvertToCurveTypeEnum(curve.CurveType);
// Emit the blob
int offset = sizeof(BCRYPT_ECC_PARAMETER_HEADER);
Interop.BCrypt.Emit(blob, ref offset, curve.Prime);
Interop.BCrypt.Emit(blob, ref offset, curve.A);
Interop.BCrypt.Emit(blob, ref offset, curve.B);
Interop.BCrypt.Emit(blob, ref offset, curve.G.X);
Interop.BCrypt.Emit(blob, ref offset, curve.G.Y);
Interop.BCrypt.Emit(blob, ref offset, curve.Order);
Interop.BCrypt.Emit(blob, ref offset, curve.Cofactor);
if (curve.Seed != null)
{
Interop.BCrypt.Emit(blob, ref offset, curve.Seed);
}
// We better have computed the right allocation size above!
Debug.Assert(offset == blobSize, "offset == blobSize");
}
return(blob);
}
