internal override NCryptKeyOrCryptProviderSafeHandle CreateKey(string keyName, int keySize, Algorithm algorithm, bool overwrite, KeyUsage keyUsage, out KeySpec keySpec)
{
const int ALREADY_EXISTS = unchecked ((int)0x8009000f);
if (algorithm != Algorithm.RSA)
{
throw new ArgumentException("CAPI does not support algorithms other than RSA.", nameof(algorithm));
}
NCryptKeyOrCryptProviderSafeHandle provider;
if (!AdvApi32.CryptAcquireContext(out provider, keyName, _providerName, ProviderType.PROV_RSA_AES, CryptAcquireContextFlags.CRYPT_NEWKEYSET))
{
var lastError = Marshal.GetLastWin32Error();
if (lastError == ALREADY_EXISTS && overwrite)
{
if (!AdvApi32.CryptAcquireContext(out provider, keyName, _providerName, ProviderType.PROV_RSA_AES, CryptAcquireContextFlags.CRYPT_DELETEKEYSET))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
if (!AdvApi32.CryptAcquireContext(out provider, keyName, _providerName, ProviderType.PROV_RSA_AES, CryptAcquireContextFlags.CRYPT_NEWKEYSET))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
else
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
var flags = CryptGenKeyFlags.CRYPT_EXPORTABLE;
var keySizeFlags = ((uint)keySize & 0xFFFFU) << 16;
var genKeyFlags = ((ushort)flags) | keySizeFlags;
CryptKeySafeHandle key;
KeySpec algorithmKeySpec;
switch (keyUsage)
{
case KeyUsage.KeyExchange:
algorithmKeySpec = KeySpec.AT_KEYEXCHANGE;
break;
case KeyUsage.Signature:
algorithmKeySpec = KeySpec.AT_SIGNATURE;
break;
default:
throw new ArgumentException(nameof(keyUsage));
}
if (!AdvApi32.CryptGenKey(provider, algorithmKeySpec, genKeyFlags, out key))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
key.Close();
keySpec = algorithmKeySpec;
return(provider);
}