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// Crypto/ZipCrypto.cpp
#include "StdAfx.h"
#include "../../../C/7zCrc.h"
#include "../Common/StreamUtils.h"
#include "RandGen.h"
#include "ZipCrypto.h"
namespace NCrypto {
namespace NZip {
void CCipher::UpdateKeys(Byte b)
{
Keys[0] = CRC_UPDATE_BYTE(Keys[0], b);
Keys[1] = (Keys[1] + (Keys[0] & 0xFF)) * 0x8088405 + 1;
Keys[2] = CRC_UPDATE_BYTE(Keys[2], (Byte)(Keys[1] >> 24));
}
STDMETHODIMP CCipher::CryptoSetPassword(const Byte *password, UInt32 passwordLen)
{
Keys[0] = 0x12345678;
Keys[1] = 0x23456789;
Keys[2] = 0x34567890;
UInt32 i;
for (i = 0; i < passwordLen; i++)
UpdateKeys(password[i]);
for (i = 0; i < 3; i++)
Keys2[i] = Keys[i];
return S_OK;
}
STDMETHODIMP CCipher::Init()
{
return S_OK;
}
Byte CCipher::DecryptByteSpec()
{
UInt32 temp = Keys[2] | 2;
return (Byte)((temp * (temp ^ 1)) >> 8);
}
HRESULT CEncoder::WriteHeader(ISequentialOutStream *outStream, UInt32 crc)
{
Byte h[kHeaderSize];
g_RandomGenerator.Generate(h, kHeaderSize - 2);
h[kHeaderSize - 1] = (Byte)(crc >> 24);
h[kHeaderSize - 2] = (Byte)(crc >> 16);
RestoreKeys();
Filter(h, kHeaderSize);
return WriteStream(outStream, h, kHeaderSize);
}
STDMETHODIMP_(UInt32) CEncoder::Filter(Byte *data, UInt32 size)
{
for (UInt32 i = 0; i < size; i++)
{
Byte b = data[i];
data[i] = (Byte)(b ^ DecryptByteSpec());;
UpdateKeys(b);
}
return size;
}
HRESULT CDecoder::ReadHeader(ISequentialInStream *inStream)
{
Byte h[kHeaderSize];
RINOK(ReadStream_FAIL(inStream, h, kHeaderSize));
RestoreKeys();
Filter(h, kHeaderSize);
return S_OK;
}
STDMETHODIMP_(UInt32) CDecoder::Filter(Byte *data, UInt32 size)
{
for (UInt32 i = 0; i < size; i++)
{
Byte c = (Byte)(data[i] ^ DecryptByteSpec());
UpdateKeys(c);
data[i] = c;
}
return size;
}
}}
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