public static ArrayLease <byte> DecryptHexToBytes(string ciphertext, ArraySegment <byte> key, out int count)
{
// Throw if the string isn't divisible by 2, since bytes are 2 hex digits
if ((ciphertext.Length & 1) != 0) // ciphertext.Length % 2 != 0
{
// TODO: Strings.resx if it's worth it (see notes above)
throw new ArgumentException(
message: "The ciphertext needs to be hex-encoded and have a length divisible by 2.",
paramName: nameof(ciphertext));
}
int bufferLength = ciphertext.Length / 2;
var rented = ArrayPool <byte> .Shared.Rent(bufferLength);
try
{
Debug.Assert(bufferLength <= rented.Length);
// Do the translation via Hexadecimal.ToByte
int i = 0, j = 0;
while (i < bufferLength)
{
rented[i] = Hexadecimal.ToByte(ciphertext[j], ciphertext[j + 1]);
i += 1;
j += 2;
}
Debug.Assert(i == bufferLength && j == i * 2);
// Now call DecryptBytes with the key/encrypted buffer
var encryptedBytes = new ArraySegment <byte>(rented, 0, bufferLength);
return(DecryptBytes(encryptedBytes, key, out count));
}
finally
{
ArrayPool <byte> .Shared.Return(rented);
}
}