internal void init(Mode aes_mode, KeySize aes_key_size, byte[] key)
{
_mode = aes_mode;
switch (aes_key_size)
{
case KeySize.Aes128:
_key_size = 16;
break;
case KeySize.Aes192:
_key_size = 24;
break;
case KeySize.Aes256:
_key_size = 32;
break;
default:
_key_size = 0;
break;
}
_counter.Zeroize();
_counter_out.Zeroize();
_keystream_pointer = 0xFFFF;
// initialize WinCrypt AES-128 key.
ms_aes_key key_blob = new ms_aes_key();
key_blob.header.bType = BlobType.PlainText;
key_blob.header.bVersion = CurrentBlobVersion;
key_blob.header.reserved = 0;
key_blob.header.aiKeyAlg = (uint)aes_key_size;
key_blob.size = _key_size;
Buffer.BlockCopy(key, 0, key_blob.key, 0, (int)key_blob.size);
int nativeKeySize;
IntPtr nativeKey = key_blob.Serialize(out nativeKeySize);
try {
bool result = Crypt32.CryptImportKey(_provider.Handle, nativeKey,
nativeKeySize, IntPtr.Zero, 0, out _key);
}
finally { Marshal.FreeCoTaskMem(nativeKey); }
_mode = aes_mode;
// WinCrypt cannot do CTR mode, we have to do it manually.
IntPtr buffer = Marshal.AllocCoTaskMem(sizeof(int));
try {
int mode = (int)((aes_mode == Mode.Ctr) ? Mode.Ecb : aes_mode);
Marshal.WriteInt32(buffer, mode);
bool result = Crypt32.CryptSetKeyParam(_key, 4 /* KP_MODE*/, buffer, 0);
}
finally { Marshal.FreeCoTaskMem(buffer); }
}