---

lubyrack.h

Go to the documentation of this file.

// lubyrack.h - written and placed in the public domain by Wei Dai

#ifndef CRYPTOPP_LUBYRACK_H
#define CRYPTOPP_LUBYRACK_H

#include "cryptlib.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

template <class T> class LRBase : public BlockTransformation, public VariableKeyLength<16, 0, UINT_MAX, 2>
{
public:
        enum {BLOCKSIZE = 2*T::DIGESTSIZE};
        unsigned int BlockSize() const {return BLOCKSIZE;}

protected:
        LRBase(const byte *userKey, unsigned int keyLen);

        enum {S=T::DIGESTSIZE};
        const unsigned int L;   // key length / 2
        SecByteBlock key;

        mutable T hm;
        mutable SecByteBlock buffer;
};

template <class T> class LREncryption : public LRBase<T>
{
public:
        // keyLen must be even
        LREncryption(const byte *userKey, int keyLen=LRBase<T>::DEFAULT_KEYLENGTH)
                : LRBase<T>(userKey, keyLen) {}

        void ProcessBlock(byte * inoutBlock) const
                {LREncryption<T>::ProcessBlock(inoutBlock, inoutBlock);}

        void ProcessBlock(const byte *inBlock, byte * outBlock) const;
};

template <class T> class LRDecryption : public LRBase<T>
{
public:
        // keyLen must be even
        LRDecryption(const byte *userKey, int keyLen=LRBase<T>::DEFAULT_KEYLENGTH)
                : LRBase<T>(userKey, keyLen) {}

        void ProcessBlock(byte * inoutBlock) const
                {LRDecryption<T>::ProcessBlock(inoutBlock, inoutBlock);}

        void ProcessBlock(const byte *inBlock, byte * outBlock) const;
};

template <class T> LRBase<T>::LRBase(const byte *userKey, unsigned int keyLen)
        : L(keyLen/2), key(2*L), buffer(2*S)
{
        memcpy(key, userKey, 2*L);
}

#define KL key
#define KR key+L
#define BL buffer
#define BR buffer+S
#define IL inBlock
#define IR inBlock+S
#define OL outBlock
#define OR outBlock+S

template <class T> void LREncryption<T>::ProcessBlock(const byte *inBlock, byte * outBlock) const
{
        hm.Update(KL, L);
        hm.Update(IL, S);
        hm.Final(BR);
        xorbuf(BR, IR, S);

        hm.Update(KR, L);
        hm.Update(BR, S);
        hm.Final(BL);
        xorbuf(BL, IL, S);

        hm.Update(KL, L);
        hm.Update(BL, S);
        hm.Final(OR);
        xorbuf(OR, BR, S);

        hm.Update(KR, L);
        hm.Update(OR, S);
        hm.Final(OL);
        xorbuf(OL, BL, S);
}

template <class T> void LRDecryption<T>::ProcessBlock(const byte *inBlock, byte * outBlock) const
{
        hm.Update(KR, L);
        hm.Update(IR, S);
        hm.Final(BL);
        xorbuf(BL, IL, S);

        hm.Update(KL, L);
        hm.Update(BL, S);
        hm.Final(BR);
        xorbuf(BR, IR, S);

        hm.Update(KR, L);
        hm.Update(BR, S);
        hm.Final(OL);
        xorbuf(OL, BL, S);

        hm.Update(KL, L);
        hm.Update(OL, S);
        hm.Final(OR);
        xorbuf(OR, BR, S);
}

#undef KL
#undef KR
#undef BL
#undef BR
#undef IL
#undef IR
#undef OL
#undef OR

NAMESPACE_END

#endif

---