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Ekey, posted Mon Jul 04, 2016 5:28 pm (15018)

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Part of code for decrypt RAS archives from game Max Payne 1/2 (Android / PC). Maybe usefull for someone

Code:

struct RASHeader
{
   DWORD dwID;
   DWORD dwSeed;
};

Code:

void DecryptWithSeed(unsigned char *pBuffer, int dwSize, int dwSeed)
{
   if (!dwSeed)
      dwSeed = 1;

   if (dwSize > 0)
   {
      char wSeed = 18;
      char pTemp;
      for (int i = 0; i       {
         dwSeed = -2 * (dwSeed / 177)   171 * (dwSeed % 177);
         pTemp = ((pBuffer[i] > (8 - i % 5))) ^ wSeed;
         wSeed  = 6;
         pBuffer[i] = pTemp   dwSeed;
      }
   }
}

aluigi, posted Tue Jul 05, 2016 3:12 pm (15036)

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Well done:
http://aluigi.org/bms/max_payne_ras.bms

The header is visible but now the last step will be to undertand that decrypted data that probably has a second pass of encryption or it's encrypted using a different seed.

Ekey, posted Tue Jul 05, 2016 6:30 pm (15045)

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Here my test tool for decrypt header and file table sample of archive inside. In the fact header must be 0x2C bytes and encrypted only 0x24 bytes from 0x8 position.

Edited: Attached variant 2

MPRASDecrypt-v2-src.rar

MPRASDecrypt-src-bin.rar

aluigi, posted Tue Jul 05, 2016 10:37 pm (15058)

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Script 0.2, complete extraction

Ekey, posted Tue Jul 05, 2016 11:30 pm (15063)

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Cool