internal static byte[] GetPrimeCurveBlob(ref ECParameters parameters, bool ecdh)
{
Debug.Assert(parameters.Curve.IsPrime);
bool includePrivateParameters = (parameters.D != null);
ECCurve curve = parameters.Curve;
byte[] blob;
unsafe
{
// We need to build a key blob structured as follows:
// BCRYPT_ECCFULLKEY_BLOB 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
// byte[cbFieldLength] Q.X
// byte[cbFieldLength] Q.Y
// -- Only if "includePrivateParameters" is true --
// byte[cbSubgroupOrder] D
int blobSize = sizeof(BCRYPT_ECCFULLKEY_BLOB) +
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) +
parameters.Q.X.Length +
parameters.Q.Y.Length;
if (includePrivateParameters)
{
blobSize += parameters.D.Length;
}
blob = new byte[blobSize];
fixed(byte *pBlob = &blob[0])
{
// Build the header
BCRYPT_ECCFULLKEY_BLOB *pBcryptBlob = (BCRYPT_ECCFULLKEY_BLOB *)pBlob;
pBcryptBlob->Version = 1; // No constant for this found in bcrypt.h
pBcryptBlob->Magic = includePrivateParameters ?
(ecdh ? KeyBlobMagicNumber.BCRYPT_ECDH_PRIVATE_GENERIC_MAGIC : KeyBlobMagicNumber.BCRYPT_ECDSA_PRIVATE_GENERIC_MAGIC) :
(ecdh ? KeyBlobMagicNumber.BCRYPT_ECDH_PUBLIC_GENERIC_MAGIC : KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_GENERIC_MAGIC);
pBcryptBlob->cbCofactor = curve.Cofactor.Length;
pBcryptBlob->cbFieldLength = parameters.Q.X.Length;
pBcryptBlob->cbSeed = curve.Seed == null ? 0 : curve.Seed.Length;
pBcryptBlob->cbSubgroupOrder = curve.Order.Length;
pBcryptBlob->CurveGenerationAlgId = GetHashAlgorithmId(curve.Hash);
pBcryptBlob->CurveType = ConvertToCurveTypeEnum(curve.CurveType);
// Emit the blob
int offset = sizeof(BCRYPT_ECCFULLKEY_BLOB);
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);
}
Interop.BCrypt.Emit(blob, ref offset, parameters.Q.X);
Interop.BCrypt.Emit(blob, ref offset, parameters.Q.Y);
if (includePrivateParameters)
{
Interop.BCrypt.Emit(blob, ref offset, parameters.D);
}
// We better have computed the right allocation size above!
Debug.Assert(offset == blobSize, "offset == blobSize");
}
return(blob);
}
}
internal static void ExportPrimeCurveParameters(ref ECParameters ecParams, byte[] ecBlob, bool includePrivateParameters)
{
// We now have a buffer laid out as follows:
// BCRYPT_ECCFULLKEY_BLOB 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
// byte[cbFieldLength] Q.X
// byte[cbFieldLength] Q.Y
// -- Private only --
// byte[cbSubgroupOrder] D
KeyBlobMagicNumber magic = (KeyBlobMagicNumber)BitConverter.ToInt32(ecBlob, 0);
// Check the magic value in the key blob header. If the blob does not have the required magic,
// then throw a CryptographicException.
CheckMagicValueOfKey(magic, includePrivateParameters);
unsafe
{
// Fail-fast if a rogue provider gave us a blob that isn't even the size of the blob header.
if (ecBlob.Length < sizeof(BCRYPT_ECCFULLKEY_BLOB))
throw ErrorCode.E_FAIL.ToCryptographicException();
fixed(byte *pEcBlob = &ecBlob[0])
{
BCRYPT_ECCFULLKEY_BLOB *pBcryptBlob = (BCRYPT_ECCFULLKEY_BLOB *)pEcBlob;
var primeCurve = new ECCurve();
primeCurve.CurveType = ConvertToCurveTypeEnum(pBcryptBlob->CurveType);
primeCurve.Hash = GetHashAlgorithmName(pBcryptBlob->CurveGenerationAlgId);
int offset = sizeof(BCRYPT_ECCFULLKEY_BLOB);
primeCurve.Prime = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength);
primeCurve.A = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength);
primeCurve.B = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength);
primeCurve.G = new ECPoint()
{
X = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength),
Y = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength),
};
primeCurve.Order = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbSubgroupOrder);
primeCurve.Cofactor = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbCofactor);
// Optional parameters
primeCurve.Seed = pBcryptBlob->cbSeed == 0 ? null : Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbSeed);
ecParams.Q = new ECPoint
{
X = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength),
Y = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbFieldLength)
};
if (includePrivateParameters)
{
ecParams.D = Interop.BCrypt.Consume(ecBlob, ref offset, pBcryptBlob->cbSubgroupOrder);
}
ecParams.Curve = primeCurve;
}
}
}
