public static bool VerifyMemeData(byte[] input, out byte[] output, MemeKeyIndex keyIndex)
{
output = null;
if (input.Length < 0x60)
{
return(false);
}
var memekey = new MemeKey(keyIndex);
output = (byte[])input.Clone();
var sigBuffer = new byte[0x60];
Array.Copy(input, input.Length - 0x60, sigBuffer, 0, 0x60);
sigBuffer = memekey.RsaPublic(sigBuffer);
using (var sha1 = SHA1.Create())
foreach (var orVal in new byte[] { 0, 0x80 })
{
sigBuffer[0x0] |= orVal;
sigBuffer.CopyTo(output, output.Length - 0x60);
memekey.AesDecrypt(output).CopyTo(output, 0);
// Check for 8-byte equality.
if (BitConverter.ToUInt64(sha1.ComputeHash(output, 0, output.Length - 0x8), 0) ==
BitConverter.ToUInt64(output, output.Length - 0x8))
{
return(true);
}
}
output = null;
return(false);
}
private static bool DecryptCompare(byte[] output, byte[] sigBuffer, MemeKey key, SHA1 sha1)
{
sigBuffer.CopyTo(output, output.Length - 0x60);
key.AesDecrypt(output).CopyTo(output, 0);
// Check for 8-byte equality.
var hash = sha1.ComputeHash(output, 0, output.Length - 0x8);
var computed = BitConverter.ToUInt64(hash, 0);
var existing = BitConverter.ToUInt64(output, output.Length - 0x8);
return(computed == existing);
}
