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https://github.com/Xevion/easy7zip.git
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66 lines
1.2 KiB
C++
Executable File
66 lines
1.2 KiB
C++
Executable File
// Crypto/ZipCrypto.cpp
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#include "StdAfx.h"
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#include "ZipCipher.h"
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#include "../../../Common/CRC.h"
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namespace NCrypto {
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namespace NZip {
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static inline UInt32 ZipCRC32(UInt32 c, Byte b)
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{
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return CCRC::Table[(c ^ b) & 0xFF] ^ (c >> 8);
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}
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void CCipher::UpdateKeys(Byte b)
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{
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Keys[0] = ZipCRC32(Keys[0], b);
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Keys[1] += Keys[0] & 0xff;
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Keys[1] = Keys[1] * 134775813L + 1;
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Keys[2] = ZipCRC32(Keys[2], Keys[1] >> 24);
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}
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void CCipher::SetPassword(const Byte *password, UInt32 passwordLength)
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{
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Keys[0] = 305419896L;
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Keys[1] = 591751049L;
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Keys[2] = 878082192L;
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for (UInt32 i = 0; i < passwordLength; i++)
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UpdateKeys(password[i]);
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}
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Byte CCipher::DecryptByteSpec()
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{
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UInt32 temp = Keys[2] | 2;
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return (temp * (temp ^ 1)) >> 8;
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}
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Byte CCipher::DecryptByte(Byte encryptedByte)
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{
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Byte c = encryptedByte ^ DecryptByteSpec();
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UpdateKeys(c);
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return c;
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}
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Byte CCipher::EncryptByte(Byte b)
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{
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Byte c = b ^ DecryptByteSpec();
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UpdateKeys(b);
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return c;
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}
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void CCipher::DecryptHeader(Byte *buffer)
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{
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for (int i = 0; i < 12; i++)
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buffer[i] = DecryptByte(buffer[i]);
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}
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void CCipher::EncryptHeader(Byte *buffer)
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{
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for (int i = 0; i < 12; i++)
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buffer[i] = EncryptByte(buffer[i]);
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}
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}}
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