127 lines
3.7 KiB
C#
127 lines
3.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Linq;
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using System.Runtime.InteropServices;
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using System.Text;
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using System.Threading.Tasks;
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namespace PspCrypto
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{
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public class AtracCrypto
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{
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const int NBYTES = 0x180;
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private static uint ROTR32(uint v, int n)
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{
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n &= 32 - 1;
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return (v >> n) | (v << (32 - n));
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}
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public static int UnscrambleAtracData(byte[] data, uint key)
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{
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int blocks = (data.Length / NBYTES) / 0x10;
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int chunks_rest = (data.Length / NBYTES) % 0x10;
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Span<uint> ptr = MemoryMarshal.Cast<byte, uint>(data);
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uint tmp2 = key;
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uint tmp;
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uint value;
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// for each block
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while (blocks > 0)
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{
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// for each chunk of block
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for (int i = 0; i < 0x10; i++)
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{
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tmp = tmp2;
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// for each value of chunk
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for (int k = 0; k < (NBYTES / 4); k++)
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{
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value = ptr[k];
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ptr[k] = tmp ^ value;
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tmp = tmp2 + (value * 123456789);
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}
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tmp2 = ROTR32(tmp2, 1);
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ptr = ptr[(NBYTES / 4)..]; // pointer on next chunk
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}
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blocks--;
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}
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// do rest chunks
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for (int i = 0; i < chunks_rest; i++)
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{
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tmp = tmp2;
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// for each value of chunk
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for (int k = 0; k < (NBYTES / 4); k++)
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{
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value = ptr[k];
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ptr[k] = tmp ^ value;
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tmp = tmp2 + (value * 123456789);
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}
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tmp2 = ROTR32(tmp2, 1);
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ptr = ptr[(NBYTES / 4)..]; // next chunk
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}
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return 0;
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}
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public static void ScrambleAtracData(Stream input, Stream output, uint key)
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{
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int blocks = (Convert.ToInt32(input.Length) / NBYTES) / 0x10;
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int chunks_rest = (Convert.ToInt32(input.Length) / NBYTES) % 0x10;
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Span<byte> block = stackalloc byte[NBYTES];
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uint tmp2 = key;
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uint tmp;
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// for each block
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while (blocks > 0)
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{
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// for each chunk of block
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for (int i = 0; i < 0x10; i++)
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{
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tmp = tmp2;
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input.Read(block);
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Span<uint> ptr = MemoryMarshal.Cast<byte, uint>(block);
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// for each value of chunk
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for (int k = 0; k < (NBYTES / 4); k++)
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{
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ptr[k] ^= tmp;
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tmp = tmp2 + (ptr[k] * 123456789);
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}
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output.Write(block);
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tmp2 = ROTR32(tmp2, 1);
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ptr = ptr[(NBYTES / 4)..]; // pointer on next chunk
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}
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blocks--;
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}
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// do rest chunks
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for (int i = 0; i < chunks_rest; i++)
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{
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tmp = tmp2;
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input.Read(block);
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Span<uint> ptr = MemoryMarshal.Cast<byte, uint>(block);
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// for each value of chunk
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for (int k = 0; k < (NBYTES / 4); k++)
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{
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ptr[k] ^= tmp;
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tmp = tmp2 + (ptr[k] * 123456789);
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}
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output.Write(block);
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tmp2 = ROTR32(tmp2, 1);
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ptr = ptr[(NBYTES / 4)..]; // next chunk
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}
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}
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}
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}
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