shark.cpp

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

#include "pch.h"
#include "shark.h"
#include "misc.h"
#include "modes.h"
#include "gf256.h"

NAMESPACE_BEGIN(CryptoPP)

static word64 SHARKTransform(word64 a)
{
        static const byte iG[8][8] = {
                0xe7, 0x30, 0x90, 0x85, 0xd0, 0x4b, 0x91, 0x41, 
                0x53, 0x95, 0x9b, 0xa5, 0x96, 0xbc, 0xa1, 0x68, 
                0x02, 0x45, 0xf7, 0x65, 0x5c, 0x1f, 0xb6, 0x52, 
                0xa2, 0xca, 0x22, 0x94, 0x44, 0x63, 0x2a, 0xa2, 
                0xfc, 0x67, 0x8e, 0x10, 0x29, 0x75, 0x85, 0x71, 
                0x24, 0x45, 0xa2, 0xcf, 0x2f, 0x22, 0xc1, 0x0e, 
                0xa1, 0xf1, 0x71, 0x40, 0x91, 0x27, 0x18, 0xa5, 
                0x56, 0xf4, 0xaf, 0x32, 0xd2, 0xa4, 0xdc, 0x71, 
        };

        word64 result=0;
        GF256 gf256(0xf5);
        for (unsigned int i=0; i<8; i++)
                for(unsigned int j=0; j<8; j++) 
                        result ^= word64(gf256.Multiply(iG[i][j], GF256::Element(a>>(56-8*j)))) << (56-8*i);
        return result;
}

void SHARK::Base::UncheckedSetKey(const byte *key, unsigned int keyLen, const NameValuePairs &params)
{
        AssertValidKeyLength(keyLen);

        m_rounds = GetRoundsAndThrowIfInvalid(params, this);
        m_roundKeys.New(m_rounds+1);

        // concatenate key enought times to fill a
        for (unsigned int i=0; i<(m_rounds+1)*8; i++)
                ((byte *)m_roundKeys.begin())[i] = key[i%keyLen];

        SHARK::Encryption e;
        e.InitForKeySetup();
        byte IV[8] = {0,0,0,0,0,0,0,0};
        CFB_Mode_ExternalCipher::Encryption cfb(e, IV);

        cfb.ProcessString((byte *)m_roundKeys.begin(), (m_rounds+1)*8);

        ConditionalByteReverse(BIG_ENDIAN_ORDER, m_roundKeys.begin(), m_roundKeys.begin(), (m_rounds+1)*8);

        m_roundKeys[m_rounds] = SHARKTransform(m_roundKeys[m_rounds]);

        if (!IsForwardTransformation())
        {
                unsigned int i;

                // transform encryption round keys into decryption round keys
                for (i=0; i<m_rounds/2; i++)
                        std::swap(m_roundKeys[i], m_roundKeys[m_rounds-i]);

                for (i=1; i<m_rounds; i++)
                        m_roundKeys[i] = SHARKTransform(m_roundKeys[i]);
        }

#ifdef IS_LITTLE_ENDIAN
        m_roundKeys[0] = ByteReverse(m_roundKeys[0]);
        m_roundKeys[m_rounds] = ByteReverse(m_roundKeys[m_rounds]);
#endif
}

// construct an SHARK_Enc object with fixed round keys, to be used to initialize actual round keys
void SHARK::Enc::InitForKeySetup()
{
        m_rounds = DEFAULT_ROUNDS;
        m_roundKeys.New(DEFAULT_ROUNDS+1);

        for (unsigned int i=0; i<DEFAULT_ROUNDS; i++)
                m_roundKeys[i] = cbox[0][i];

        m_roundKeys[DEFAULT_ROUNDS] = SHARKTransform(cbox[0][DEFAULT_ROUNDS]);

#ifdef IS_LITTLE_ENDIAN
        m_roundKeys[0] = ByteReverse(m_roundKeys[0]);
        m_roundKeys[m_rounds] = ByteReverse(m_roundKeys[m_rounds]);
#endif
}

typedef word64 ArrayOf256Word64s[256];

template <const byte *sbox, const ArrayOf256Word64s *cbox>
struct SharkProcessAndXorBlock{         // VC60 workaround: problem with template functions
inline SharkProcessAndXorBlock(const word64 *roundKeys, unsigned int rounds, const byte *inBlock, const byte *xorBlock, byte *outBlock)
{
        word64 tmp = *(word64 *)inBlock ^ roundKeys[0];

        ByteOrder order = GetNativeByteOrder();
        tmp = cbox[0][GetByte(order, tmp, 0)] ^ cbox[1][GetByte(order, tmp, 1)] 
                ^ cbox[2][GetByte(order, tmp, 2)] ^ cbox[3][GetByte(order, tmp, 3)] 
                ^ cbox[4][GetByte(order, tmp, 4)] ^ cbox[5][GetByte(order, tmp, 5)] 
                ^ cbox[6][GetByte(order, tmp, 6)] ^ cbox[7][GetByte(order, tmp, 7)]
                ^ roundKeys[1];

        for(unsigned int i=2; i<rounds; i++) 
        {
                tmp = cbox[0][GETBYTE(tmp, 7)] ^ cbox[1][GETBYTE(tmp, 6)] 
                        ^ cbox[2][GETBYTE(tmp, 5)] ^ cbox[3][GETBYTE(tmp, 4)] 
                        ^ cbox[4][GETBYTE(tmp, 3)] ^ cbox[5][GETBYTE(tmp, 2)] 
                        ^ cbox[6][GETBYTE(tmp, 1)] ^ cbox[7][GETBYTE(tmp, 0)]
                        ^ roundKeys[i];
        }

        PutBlock<byte, BigEndian>(xorBlock, outBlock)
                (sbox[GETBYTE(tmp, 7)])
                (sbox[GETBYTE(tmp, 6)])
                (sbox[GETBYTE(tmp, 5)])
                (sbox[GETBYTE(tmp, 4)])
                (sbox[GETBYTE(tmp, 3)])
                (sbox[GETBYTE(tmp, 2)])
                (sbox[GETBYTE(tmp, 1)])
                (sbox[GETBYTE(tmp, 0)]);

        *(word64 *)outBlock ^= roundKeys[rounds];
}};

void SHARK::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        SharkProcessAndXorBlock<sbox, cbox>(m_roundKeys, m_rounds, inBlock, xorBlock, outBlock);
}

void SHARK::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        SharkProcessAndXorBlock<sbox, cbox>(m_roundKeys, m_rounds, inBlock, xorBlock, outBlock);
}

NAMESPACE_END