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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 {
#define UPDATE_KEYS(b) { \
Key0 = CRC_UPDATE_BYTE(Key0, b); \
Key1 = (Key1 + (Key0 & 0xFF)) * 0x8088405 + 1; \
Key2 = CRC_UPDATE_BYTE(Key2, (Byte)(Key1 >> 24)); } \
#define DECRYPT_BYTE_1 UInt32 temp = Key2 | 2;
#define DECRYPT_BYTE_2 ((Byte)((temp * (temp ^ 1)) >> 8))
STDMETHODIMP CCipher::CryptoSetPassword(const Byte *data, UInt32 size)
{
UInt32 Key0 = 0x12345678;
UInt32 Key1 = 0x23456789;
UInt32 Key2 = 0x34567890;
for (UInt32 i = 0; i < size; i++)
UPDATE_KEYS(data[i]);
KeyMem0 = Key0;
KeyMem1 = Key1;
KeyMem2 = Key2;
return S_OK;
}
STDMETHODIMP CCipher::Init()
{
return S_OK;
}
HRESULT CEncoder::WriteHeader_Check16(ISequentialOutStream *outStream, UInt16 crc)
{
Byte h[kHeaderSize];
/* PKZIP before 2.0 used 2 byte CRC check.
PKZIP 2.0+ used 1 byte CRC check. It's more secure.
We also use 1 byte CRC. */
g_RandomGenerator.Generate(h, kHeaderSize - 1);
// h[kHeaderSize - 2] = (Byte)(crc);
h[kHeaderSize - 1] = (Byte)(crc >> 8);
RestoreKeys();
Filter(h, kHeaderSize);
return WriteStream(outStream, h, kHeaderSize);
}
STDMETHODIMP_(UInt32) CEncoder::Filter(Byte *data, UInt32 size)
{
UInt32 Key0 = this->Key0;
UInt32 Key1 = this->Key1;
UInt32 Key2 = this->Key2;
for (UInt32 i = 0; i < size; i++)
{
Byte b = data[i];
DECRYPT_BYTE_1
data[i] = (Byte)(b ^ DECRYPT_BYTE_2);
UPDATE_KEYS(b);
}
this->Key0 = Key0;
this->Key1 = Key1;
this->Key2 = Key2;
return size;
}
HRESULT CDecoder::ReadHeader(ISequentialInStream *inStream)
{
return ReadStream_FAIL(inStream, _header, kHeaderSize);
}
void CDecoder::Init_BeforeDecode()
{
RestoreKeys();
Filter(_header, kHeaderSize);
}
STDMETHODIMP_(UInt32) CDecoder::Filter(Byte *data, UInt32 size)
{
UInt32 Key0 = this->Key0;
UInt32 Key1 = this->Key1;
UInt32 Key2 = this->Key2;
for (UInt32 i = 0; i < size; i++)
{
DECRYPT_BYTE_1
Byte b = (Byte)(data[i] ^ DECRYPT_BYTE_2);
UPDATE_KEYS(b);
data[i] = b;
}
this->Key0 = Key0;
this->Key1 = Key1;
this->Key2 = Key2;
return size;
}
}}
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