rar20crypto.cpp

来自「7z一个高压缩比的压缩程序源代码,重要的是里面的算法值得学习」· C++ 代码 · 共 137 行

// Crypto/Rar20Crypto.cpp

#include "StdAfx.h"

extern "C"
{
  #include "../../../C/7zCrc.h"
  #include "../../../C/CpuArch.h"
  #include "../../../C/RotateDefs.h"
}

#include "Rar20Crypto.h"

namespace NCrypto {
namespace NRar20 {

static const int kNumRounds = 32;

static const Byte InitSubstTable[256] = {
  215, 19,149, 35, 73,197,192,205,249, 28, 16,119, 48,221,  2, 42,
  232,  1,177,233, 14, 88,219, 25,223,195,244, 90, 87,239,153,137,
  255,199,147, 70, 92, 66,246, 13,216, 40, 62, 29,217,230, 86,  6,
   71, 24,171,196,101,113,218,123, 93, 91,163,178,202, 67, 44,235,
  107,250, 75,234, 49,167,125,211, 83,114,157,144, 32,193,143, 36,
  158,124,247,187, 89,214,141, 47,121,228, 61,130,213,194,174,251,
   97,110, 54,229,115, 57,152, 94,105,243,212, 55,209,245, 63, 11,
  164,200, 31,156, 81,176,227, 21, 76, 99,139,188,127, 17,248, 51,
  207,120,189,210,  8,226, 41, 72,183,203,135,165,166, 60, 98,  7,
  122, 38,155,170, 69,172,252,238, 39,134, 59,128,236, 27,240, 80,
  131,  3, 85,206,145, 79,154,142,159,220,201,133, 74, 64, 20,129,
  224,185,138,103,173,182, 43, 34,254, 82,198,151,231,180, 58, 10,
  118, 26,102, 12, 50,132, 22,191,136,111,162,179, 45,  4,148,108,
  161, 56, 78,126,242,222, 15,175,146, 23, 33,241,181,190, 77,225,
    0, 46,169,186, 68, 95,237, 65, 53,208,253,168,  9, 18,100, 52,
  116,184,160, 96,109, 37, 30,106,140,104,150,  5,204,117,112, 84
};

void CData::UpdateKeys(const Byte *data)
{
  for (int i = 0; i < 16; i += 4)
    for (int j = 0; j < 4; j++)
      Keys[j] ^= g_CrcTable[data[i + j]];
}

static void Swap(Byte *b1, Byte *b2)
{
  Byte b = *b1;
  *b1 = *b2;
  *b2 = b;
}

void CData::SetPassword(const Byte *password, UInt32 passwordLen)
{
  Keys[0] = 0xD3A3B879L;
  Keys[1] = 0x3F6D12F7L;
  Keys[2] = 0x7515A235L;
  Keys[3] = 0xA4E7F123L;
  
  Byte psw[256];
  memset(psw, 0, sizeof(psw));
  memcpy(psw, password, passwordLen);
  memcpy(SubstTable, InitSubstTable, sizeof(SubstTable));

  for (UInt32 j = 0; j < 256; j++)
    for (UInt32 i = 0; i < passwordLen; i += 2)
    {
      UInt32 n2 = (Byte)g_CrcTable[(psw[i + 1] + j) & 0xFF];
      UInt32 n1 = (Byte)g_CrcTable[(psw[i] - j) & 0xFF];
      for (UInt32 k = 1; (n1 & 0xFF) != n2; n1++, k++)
        Swap(&SubstTable[n1 & 0xFF], &SubstTable[(n1 + i + k) & 0xFF]);
    }
  for (UInt32 i = 0; i < passwordLen; i+= 16)
    EncryptBlock(&psw[i]);
}

void CData::CryptBlock(Byte *buf, bool encrypt)
{
  Byte inBuf[16];
  UInt32 A, B, C, D, T, TA, TB;

  A = GetUi32(buf +  0) ^ Keys[0];
  B = GetUi32(buf +  4) ^ Keys[1];
  C = GetUi32(buf +  8) ^ Keys[2];
  D = GetUi32(buf + 12) ^ Keys[3];

  if (!encrypt)
    memcpy(inBuf, buf, sizeof(inBuf));
  
  for (int i = 0; i < kNumRounds; i++)
  {
    UInt32 key = Keys[(encrypt ? i : (kNumRounds - 1 - i)) & 3];
    T = ((C + rotlFixed(D, 11)) ^ key);
    TA = A ^ SubstLong(T);
    T = ((D ^ rotlFixed(C, 17)) + key);
    TB = B ^ SubstLong(T);
    A = C;
    B = D;
    C = TA;
    D = TB;
  }

  SetUi32(buf +  0, C ^ Keys[0]);
  SetUi32(buf +  4, D ^ Keys[1]);
  SetUi32(buf +  8, A ^ Keys[2]);
  SetUi32(buf + 12, B ^ Keys[3]);

  UpdateKeys(encrypt ? buf : inBuf);
}

STDMETHODIMP CDecoder::CryptoSetPassword(const Byte *data, UInt32 size)
{
  _cipher.SetPassword(data, size);
  return S_OK;
}

STDMETHODIMP CDecoder::Init()
{
  return S_OK;
}

static const UInt32 kBlockSize = 16;

STDMETHODIMP_(UInt32) CDecoder::Filter(Byte *data, UInt32 size)
{
  if (size == 0)
    return 0;
  if (size < kBlockSize)
    return kBlockSize;
  UInt32 i;
  size -= kBlockSize;
  for (i = 0; i <= size; i += kBlockSize)
    _cipher.DecryptBlock(data + i);
  return i;
}

}}