//this returns an empty buffer if error
public byte[] Decrypt(byte[] input, out int length)
{
int version, len = input.Length;
if (len < 261)
{
length = 0; return(new byte[] { });
}
else
{
int mod_size = len % 256;
if (mod_size == 32)
{
version = 1;
}
else if (mod_size == 33)
{
version = 2;
}
else if (mod_size == 5)
{
version = 3;
}
else
{
length = 0; return(new byte[] { });
}
}
byte[] cipher8, output;
int output_len;
if (version == 1)
{
output_len = len - 32;
output = new byte[output_len];
Buffer.BlockCopy(input, 32, output, 0, output_len);
cipher8 = cipher8_from_iv(input);
}
else if (version == 2)
{
output_len = len - 33;
output = new byte[output_len];
Buffer.BlockCopy(input, 32, output, 0, output_len);
cipher8 = cipher8_from_iv(input);
}
else
{
output_len = len - 5;
output = new byte[output_len];
Buffer.BlockCopy(input, 4, output, 0, output_len);
byte[] tmp = new byte[4];
Buffer.BlockCopy(input, 0, tmp, 0, 4);
Array.Reverse(tmp);
uint ms = BitConverter.ToUInt32(tmp, 0);
cipher8 = cipher8_from_rand(ref ms);
if (input[len - 1] != make_integrity_byte(gen_rand(ref ms)))
{
length = 0; return(new byte[] { });
}
}
Collection <byte[]> outputcontent = new Collection <byte[]>();
//break into chunks of 256
int roundedsize = (output_len + 255) / 256; //round up
for (int i = 0; i < roundedsize; i++)
{
outputcontent.Add(new byte[256]);
}
for (int i = 0; i < output_len; i++)
{
outputcontent[i / 256][i % 256] = output[i];
}
for (int i = 0; i < outputcontent.Count; i++)
{
uint[] temp2 = new uint[0x100 / 4];
uint[] temp3 = new uint[0x100 / 4];
Buffer.BlockCopy(outputcontent[i], 0, temp2, 0, 0x100);
Buffer.BlockCopy(temp2, 0, temp3, 0, 0x100);
if (version == 1)
{
Shuffles.Unshuffle(temp2);
}
else
{
Shuffles.Unshuffle2(temp2);
}
Buffer.BlockCopy(temp2, 0, outputcontent[i], 0, 0x100);
for (int j = 0; j < 256; j++)
{
outputcontent[i][j] ^= cipher8[j];
}
Buffer.BlockCopy(temp3, 0, cipher8, 0, 0x100);
}
byte[] ret = new byte[output_len];
for (int i = 0; i < outputcontent.Count; i++)
{
Buffer.BlockCopy(outputcontent[i], 0, ret, i * 256, 0x100);
}
length = output_len - ret.Last();
return(ret);
}
//this returns an empty buffer if error
public static byte[] Decrypt(byte[] input, out int length)
{
int version, len = input.Length;
if (len < 261)
{
length = 0;
return(new byte[] { });
}
var modSize = len % 256;
switch (modSize)
{
case 32:
version = 1;
break;
case 33:
version = 2;
break;
case 5:
version = 3;
break;
default:
length = 0; return(new byte[] { });
}
byte[] cipher8, output;
int outputLen;
switch (version)
{
case 1:
outputLen = len - 32;
output = new byte[outputLen];
Buffer.BlockCopy(input, 32, output, 0, outputLen);
cipher8 = Cipher8FromIv(input);
break;
case 2:
outputLen = len - 33;
output = new byte[outputLen];
Buffer.BlockCopy(input, 32, output, 0, outputLen);
cipher8 = Cipher8FromIv(input);
break;
default:
outputLen = len - 5;
output = new byte[outputLen];
Buffer.BlockCopy(input, 4, output, 0, outputLen);
var tmp = new byte[4];
Buffer.BlockCopy(input, 0, tmp, 0, 4);
Array.Reverse(tmp);
var ms = BitConverter.ToUInt32(tmp, 0);
cipher8 = Cipher8FromRand(ref ms);
if (input[len - 1] != MakeIntegrityByte(GenerateRand(ref ms)))
{
length = 0; return(new byte[] { });
}
break;
}
var outputcontent = new Collection <byte[]>();
//break into chunks of 256
var roundedsize = (outputLen + 255) / 256; //round up
for (var i = 0; i < roundedsize; i++)
{
outputcontent.Add(new byte[256]);
}
for (var i = 0; i < outputLen; i++)
{
outputcontent[i / 256][i % 256] = output[i];
}
foreach (var bytes in outputcontent)
{
var temp2 = new uint[0x100 / 4];
var temp3 = new uint[0x100 / 4];
Buffer.BlockCopy(bytes, 0, temp2, 0, 0x100);
Buffer.BlockCopy(temp2, 0, temp3, 0, 0x100);
if (version == 1)
{
Shuffles.Unshuffle(temp2);
}
else
{
Shuffles.Unshuffle2(temp2);
}
Buffer.BlockCopy(temp2, 0, bytes, 0, 0x100);
for (var j = 0; j < 256; j++)
{
bytes[j] ^= cipher8[j];
}
Buffer.BlockCopy(temp3, 0, cipher8, 0, 0x100);
}
var ret = new byte[outputLen];
for (var i = 0; i < outputcontent.Count; i++)
{
Buffer.BlockCopy(outputcontent[i], 0, ret, i * 256, 0x100);
}
length = outputLen - ret.Last();
return(ret);
}