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(EAGLS): auto-detect CG archive encryption scheme.
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morkt
parent
10e3846f51
commit
dbd95d62e3
@ -2,7 +2,7 @@
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//! \date Fri May 15 02:52:04 2015
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//! \brief EAGLS system resource archives.
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//
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// Copyright (C) 2015 by morkt
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// Copyright (C) 2015-2016 by morkt
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to
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@ -27,6 +27,7 @@ using System;
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using System.Collections.Generic;
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using System.ComponentModel.Composition;
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using System.IO;
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using System.Linq;
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using GameRes.Utility;
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namespace GameRes.Formats.Eagls
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@ -45,8 +46,11 @@ namespace GameRes.Formats.Eagls
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Extensions = new string[] { "pak" };
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}
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static readonly string IndexKey = "1qaz2wsx3edc4rfv5tgb6yhn7ujm8ik,9ol.0p;/-@:^[]";
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static readonly string Key = "EAGLS_SYSTEM";
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internal static readonly string IndexKey = "1qaz2wsx3edc4rfv5tgb6yhn7ujm8ik,9ol.0p;/-@:^[]";
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internal static readonly string Key = "EAGLS_SYSTEM";
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// FIXME not thread-safe
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CRuntimeRandomGenerator m_rng = new CRuntimeRandomGenerator();
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public override ArcFile TryOpen (ArcView file)
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{
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@ -94,45 +98,31 @@ namespace GameRes.Formats.Eagls
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}
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if (0 == dir.Count)
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return null;
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return new ArcFile (file, this, dir);
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if (dir[0].Name.EndsWith (".gr", StringComparison.InvariantCultureIgnoreCase)) // CG archive
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return new CgArchive (file, this, dir);
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else
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return new ArcFile (file, this, dir);
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}
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public override Stream OpenEntry (ArcFile arc, Entry entry)
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{
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if (entry.Name.EndsWith (".gr", StringComparison.InvariantCultureIgnoreCase))
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return DecryptGr (arc, entry);
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var cg_arc = arc as CgArchive;
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if (null != cg_arc)
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return cg_arc.DecryptEntry (entry);
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if (entry.Name.EndsWith (".dat", StringComparison.InvariantCultureIgnoreCase))
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return DecryptDat (arc, entry);
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return arc.File.CreateStream (entry.Offset, entry.Size);
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}
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Stream DecryptGr (ArcFile arc, Entry entry)
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{
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var input = new byte[entry.Size];
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arc.File.View.Read (entry.Offset, input, 0, entry.Size);
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int seed = 0x75bd924 ^ input[input.Length-1];
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int limit = Math.Min (input.Length-1, 0x174b);
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for (int i = 0; i < limit; ++i)
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{
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seed = LRand (seed);
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int index = (int)(seed * 4.656612875245797e-10 * 256);
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input[i] ^= (byte)Key[index % Key.Length];
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}
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return new MemoryStream (input);
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}
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Stream DecryptDat (ArcFile arc, Entry entry)
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{
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byte[] input = new byte[entry.Size];
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arc.File.View.Read (entry.Offset, input, 0, entry.Size);
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byte[] input = arc.File.View.ReadBytes (entry.Offset, entry.Size);
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int text_offset = 3600;
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int text_length = (int)(entry.Size - text_offset - 2);
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int seed = (sbyte)input[input.Length-1];
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m_rng.SRand ((sbyte)input[input.Length-1]);
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for (int i = 0; i < text_length; i += 2)
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{
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seed = seed * 0x343FD + 0x269EC3;
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int index = (int)(((uint)seed >> 16) & 0x7fff);
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input[text_offset + i] ^= (byte)Key[index % Key.Length];
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input[text_offset + i] ^= (byte)Key[m_rng.Rand() % Key.Length];
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}
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return new MemoryStream (input);
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}
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@ -144,15 +134,13 @@ namespace GameRes.Formats.Eagls
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using (var view = idx.CreateViewAccessor (0, (uint)idx.MaxOffset))
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unsafe
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{
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uint seed = view.ReadUInt32 (idx_size);
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m_rng.SRand (view.ReadInt32 (idx_size));
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byte* ptr = view.GetPointer (0);
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try
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{
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for (int i = 0; i < idx_size; ++i)
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{
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seed = seed * 0x343FD + 0x269EC3;
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int index = (int)(seed >> 16) & 0x7FFF;
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output[i] = (byte)(ptr[i] ^ IndexKey[index % IndexKey.Length]);
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output[i] = (byte)(ptr[i] ^ IndexKey[m_rng.Rand() % IndexKey.Length]);
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}
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return output;
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}
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@ -162,17 +150,97 @@ namespace GameRes.Formats.Eagls
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}
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}
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}
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}
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int LRand (int seed)
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internal interface IRandomGenerator
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{
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void SRand (int seed);
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int Rand ();
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}
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internal class CRuntimeRandomGenerator : IRandomGenerator
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{
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uint m_seed;
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public void SRand (int seed)
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{
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const int A = 48271;
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const int Q = 44488;
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const int R = 3399;
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const int M = 2147483647;
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seed = A * (seed % Q) - R * (seed / Q);
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if (seed < 0)
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seed += M;
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return seed;
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m_seed = (uint)seed;
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}
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public int Rand ()
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{
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m_seed = m_seed * 214013u + 2531011u;
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return (int)(m_seed >> 16) & 0x7FFF;
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}
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}
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internal class LehmerRandomGenerator : IRandomGenerator
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{
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int m_seed;
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const int A = 48271;
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const int Q = 44488;
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const int R = 3399;
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const int M = 2147483647;
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public void SRand (int seed)
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{
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m_seed = seed ^ 123459876;
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}
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public int Rand ()
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{
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m_seed = A * (m_seed % Q) - R * (m_seed / Q);
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if (m_seed < 0)
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m_seed += M;
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return (int)(m_seed * 4.656612875245797e-10 * 256);
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}
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}
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internal class CgArchive : ArcFile
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{
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IRandomGenerator m_rng;
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public CgArchive (ArcView arc, ArchiveFormat impl, ICollection<Entry> dir)
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: base (arc, impl, dir)
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{
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m_rng = DetectEncryptionScheme();
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}
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IRandomGenerator DetectEncryptionScheme ()
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{
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var first_entry = Dir.First();
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int signature = (File.View.ReadInt32 (first_entry.Offset) >> 8) & 0xFFFF;
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byte seed = File.View.ReadByte (first_entry.Offset+first_entry.Size-1);
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IRandomGenerator[] rng_list = {
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new LehmerRandomGenerator(),
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new CRuntimeRandomGenerator(),
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};
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foreach (var rng in rng_list)
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{
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rng.SRand (seed);
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rng.Rand(); // skip LZSS control byte
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int test = signature;
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test ^= PakOpener.Key[rng.Rand() % PakOpener.Key.Length];
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test ^= PakOpener.Key[rng.Rand() % PakOpener.Key.Length] << 8;
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// FIXME
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// as key is rather short, this detection could produce false results sometimes
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if (0x4D42 == test) // 'BM'
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return rng;
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}
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throw new UnknownEncryptionScheme();
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}
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public Stream DecryptEntry (Entry entry)
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{
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var input = File.View.ReadBytes (entry.Offset, entry.Size);
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m_rng.SRand (input[input.Length-1]);
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int limit = Math.Min (input.Length-1, 0x174b);
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for (int i = 0; i < limit; ++i)
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{
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input[i] ^= (byte)PakOpener.Key[m_rng.Rand() % PakOpener.Key.Length];
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}
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return new MemoryStream (input);
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}
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}
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}
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@ -328,6 +328,7 @@ Warusa<br/>
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<tr class="odd"><td>*.mgd<br/>*.mgs</td><td><tt>MGD</tt><br/><tt>MGS</tt></td><td>No</td><td rowspan="2">MEGU</td><td rowspan="2">Seduce</tr>
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<tr class="odd"><td>*.agc</td><td><tt>AGd</tt></td><td>No</td></tr>
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<tr><td>*.pak+*.idx</td><td>-</td><td>No</td><td rowspan="2">EAGLS</td><td rowspan="2">
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Futago Hinyuu x 3<br/>
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Oppai Baka<br/>
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Mainichi Shabutte Ii Desu ka?<br/>
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Senpai - Oppai - Kako ni Modori Pai<br/>
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