cryptopp-cmake/arc4.cpp at master · 0Knowledge/cryptopp-cmake · GitHub

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// arc4.cpp - written and placed in the public domain by Wei Dai

// The ARC4 algorithm was first revealed in an anonymous email to the

// cypherpunks mailing list. This file originally contained some

// code copied from this email. The code has since been rewritten in order

// to clarify the copyright status of this file. It should now be

// completely in the public domain.

#include "pch.h"

#define CRYPTOPP_ENABLE_NAMESPACE_WEAK 1

#include "arc4.h"

NAMESPACE_BEGIN(CryptoPP)

namespace Weak1 {

void ARC4_TestInstantiations()

{

ARC4 x;

}

ARC4_Base::~ARC4_Base()

{

m_x = m_y = 0;

}

void ARC4_Base::UncheckedSetKey(const byte *key, unsigned int keyLen, const NameValuePairs &params)

{

AssertValidKeyLength(keyLen);

m_x = 1;

m_y = 0;

unsigned int i;

for (i=0; i<256; i++)

m_state[i] = i;

unsigned int keyIndex = 0, stateIndex = 0;

for (i=0; i<256; i++)

{

unsigned int a = m_state[i];

stateIndex += key[keyIndex] + a;

stateIndex &= 0xff;

m_state[i] = m_state[stateIndex];

m_state[stateIndex] = a;

if (++keyIndex >= keyLen)

keyIndex = 0;

}

int discardBytes = params.GetIntValueWithDefault("DiscardBytes", GetDefaultDiscardBytes());

DiscardBytes(discardBytes);

}

template <class T>

static inline unsigned int MakeByte(T &x, T &y, byte *s)

{

unsigned int a = s[x];

y = (y+a) & 0xff;

unsigned int b = s[y];

s[x] = b;

s[y] = a;

x = (x+1) & 0xff;

return s[(a+b) & 0xff];

}

void ARC4_Base::GenerateBlock(byte *output, size_t size)

{

while (size--)

*output++ = MakeByte(m_x, m_y, m_state);

}

void ARC4_Base::ProcessData(byte *outString, const byte *inString, size_t length)

{

if (length == 0)

return;

byte *const s = m_state;

unsigned int x = m_x;

unsigned int y = m_y;

if (inString == outString)

{

*outString++ ^= MakeByte(x, y, s);

} while (--length);

}

else

{

*outString++ = *inString++ ^ MakeByte(x, y, s);

}

while(--length);

}

m_x = x;

m_y = y;

}

void ARC4_Base::DiscardBytes(size_t length)

{

if (length == 0)

return;

byte *const s = m_state;

unsigned int x = m_x;

unsigned int y = m_y;

{

MakeByte(x, y, s);

}

while(--length);

m_x = x;

m_y = y;

}

NAMESPACE_END

cryptopp-cmake/arc4.cpp at master · 0Knowledge/cryptopp-cmake · GitHub

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