protected override PublicKey BuildPublicKey()
{
ECParameters ecParameters = _key.ExportParameters(false);
if (!ecParameters.Curve.IsNamed)
{
throw new InvalidOperationException(SR.GetString(SR.Cryptography_ECC_NamedCurvesOnly));
}
string curveOid = ecParameters.Curve.Oid.Value;
if (string.IsNullOrEmpty(curveOid))
{
string friendlyName = ecParameters.Curve.Oid.FriendlyName;
// Translate the three curves that were supported Windows 7-8.1, but emit no Oid.Value;
// otherwise just wash the friendly name back through Oid to see if we can get a value.
switch (friendlyName)
{
case "nistP256":
curveOid = Oids.EccCurveSecp256r1;
break;
case "nistP384":
curveOid = Oids.EccCurveSecp384r1;
break;
case "nistP521":
curveOid = Oids.EccCurveSecp521r1;
break;
default:
curveOid = new Oid(friendlyName).Value;
break;
}
}
Debug.Assert(ecParameters.Q.X.Length == ecParameters.Q.Y.Length);
byte[] uncompressedPoint = new byte[1 + ecParameters.Q.X.Length + ecParameters.Q.Y.Length];
// Uncompressed point (0x04)
uncompressedPoint[0] = 0x04;
Buffer.BlockCopy(ecParameters.Q.X, 0, uncompressedPoint, 1, ecParameters.Q.X.Length);
Buffer.BlockCopy(ecParameters.Q.Y, 0, uncompressedPoint, 1 + ecParameters.Q.X.Length, ecParameters.Q.Y.Length);
Oid ecPublicKey = new Oid(Oids.Ecc);
return(new PublicKey(
ecPublicKey,
new AsnEncodedData(ecPublicKey, DerEncoder.EncodeOid(curveOid)),
new AsnEncodedData(ecPublicKey, uncompressedPoint)));
}
