121 lines
2.1 KiB
C++
121 lines
2.1 KiB
C++
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// arc4.cpp - written and placed in the public domain by Wei Dai
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// The ARC4 algorithm was first revealed in an anonymous email to the
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// cypherpunks mailing list. This file originally contained some
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// code copied from this email. The code has since been rewritten in order
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// to clarify the copyright status of this file. It should now be
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// completely in the public domain.
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#include "pch.h"
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#define CRYPTOPP_ENABLE_NAMESPACE_WEAK 1
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#include "arc4.h"
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NAMESPACE_BEGIN(CryptoPP)
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namespace Weak1 {
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void ARC4_TestInstantiations()
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{
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ARC4 x;
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}
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ARC4_Base::~ARC4_Base()
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{
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m_x = m_y = 0;
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}
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void ARC4_Base::UncheckedSetKey(const byte *key, unsigned int keyLen, const NameValuePairs ¶ms)
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{
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AssertValidKeyLength(keyLen);
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m_x = 1;
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m_y = 0;
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unsigned int i;
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for (i=0; i<256; i++)
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m_state[i] = i;
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unsigned int keyIndex = 0, stateIndex = 0;
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for (i=0; i<256; i++)
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{
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unsigned int a = m_state[i];
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stateIndex += key[keyIndex] + a;
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stateIndex &= 0xff;
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m_state[i] = m_state[stateIndex];
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m_state[stateIndex] = a;
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if (++keyIndex >= keyLen)
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keyIndex = 0;
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}
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int discardBytes = params.GetIntValueWithDefault("DiscardBytes", GetDefaultDiscardBytes());
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DiscardBytes(discardBytes);
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}
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template <class T>
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static inline unsigned int MakeByte(T &x, T &y, byte *s)
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{
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unsigned int a = s[x];
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y = (y+a) & 0xff;
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unsigned int b = s[y];
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s[x] = b;
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s[y] = a;
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x = (x+1) & 0xff;
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return s[(a+b) & 0xff];
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}
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void ARC4_Base::GenerateBlock(byte *output, size_t size)
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{
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while (size--)
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*output++ = MakeByte(m_x, m_y, m_state);
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}
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void ARC4_Base::ProcessData(byte *outString, const byte *inString, size_t length)
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{
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if (length == 0)
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return;
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byte *const s = m_state;
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unsigned int x = m_x;
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unsigned int y = m_y;
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if (inString == outString)
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{
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do
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{
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*outString++ ^= MakeByte(x, y, s);
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} while (--length);
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}
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else
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{
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do
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{
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*outString++ = *inString++ ^ MakeByte(x, y, s);
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}
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while(--length);
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}
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m_x = x;
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m_y = y;
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}
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void ARC4_Base::DiscardBytes(size_t length)
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{
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if (length == 0)
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return;
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byte *const s = m_state;
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unsigned int x = m_x;
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unsigned int y = m_y;
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do
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{
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MakeByte(x, y, s);
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}
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while(--length);
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m_x = x;
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m_y = y;
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}
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}
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NAMESPACE_END
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