serpent.cpp

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

#include "pch.h"
#include "serpent.h"
#include "misc.h"

#include "serpentp.h"

NAMESPACE_BEGIN(CryptoPP)

void Serpent_KeySchedule(word32 *k, unsigned int rounds, const byte *userKey, size_t keylen)
{
        FixedSizeSecBlock<word32, 8> k0;
        GetUserKey(LITTLE_ENDIAN_ORDER, k0.begin(), 8, userKey, keylen);
        if (keylen < 32)
                k0[keylen/4] |= word32(1) << ((keylen%4)*8);

        word32 t = k0[7];
        unsigned int i;
        for (i = 0; i < 8; ++i)
                k[i] = k0[i] = t = rotlFixed(k0[i] ^ k0[(i+3)%8] ^ k0[(i+5)%8] ^ t ^ 0x9e3779b9 ^ i, 11);
        for (i = 8; i < 4*(rounds+1); ++i)
                k[i] = t = rotlFixed(k[i-8] ^ k[i-5] ^ k[i-3] ^ t ^ 0x9e3779b9 ^ i, 11);
        k -= 20;

        word32 a,b,c,d,e;
        for (i=0; i<rounds/8; i++)
        {
                afterS2(LK); afterS2(S3); afterS3(SK);
                afterS1(LK); afterS1(S2); afterS2(SK);
                afterS0(LK); afterS0(S1); afterS1(SK);
                beforeS0(LK); beforeS0(S0); afterS0(SK);
                k += 8*4;
                afterS6(LK); afterS6(S7); afterS7(SK);
                afterS5(LK); afterS5(S6); afterS6(SK);
                afterS4(LK); afterS4(S5); afterS5(SK);
                afterS3(LK); afterS3(S4); afterS4(SK);
        }
        afterS2(LK); afterS2(S3); afterS3(SK);
}

void Serpent::Base::UncheckedSetKey(const byte *userKey, unsigned int keylen, const NameValuePairs &)
{
        AssertValidKeyLength(keylen);
        Serpent_KeySchedule(m_key, 32, userKey, keylen);
}

typedef BlockGetAndPut<word32, LittleEndian> Block;

void Serpent::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 a, b, c, d, e;
        
        Block::Get(inBlock)(a)(b)(c)(d);

        const word32 *k = m_key;
        unsigned int i=1;

        do
        {
                beforeS0(KX); beforeS0(S0); afterS0(LT);
                afterS0(KX); afterS0(S1); afterS1(LT);
                afterS1(KX); afterS1(S2); afterS2(LT);
                afterS2(KX); afterS2(S3); afterS3(LT);
                afterS3(KX); afterS3(S4); afterS4(LT);
                afterS4(KX); afterS4(S5); afterS5(LT);
                afterS5(KX); afterS5(S6); afterS6(LT);
                afterS6(KX); afterS6(S7);

                if (i == 4)
                        break;

                ++i;
                c = b;
                b = e;
                e = d;
                d = a;
                a = e;
                k += 32;
                beforeS0(LT);
        }
        while (true);

        afterS7(KX);
        
        Block::Put(xorBlock, outBlock)(d)(e)(b)(a);
}

void Serpent::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 a, b, c, d, e;
        
        Block::Get(inBlock)(a)(b)(c)(d);

        const word32 *k = m_key + 96;
        unsigned int i=4;

        beforeI7(KX);
        goto start;

        do
        {
                c = b;
                b = d;
                d = e;
                k -= 32;
                beforeI7(ILT);
start:
                            beforeI7(I7); afterI7(KX); 
                afterI7(ILT); afterI7(I6); afterI6(KX); 
                afterI6(ILT); afterI6(I5); afterI5(KX); 
                afterI5(ILT); afterI5(I4); afterI4(KX); 
                afterI4(ILT); afterI4(I3); afterI3(KX); 
                afterI3(ILT); afterI3(I2); afterI2(KX); 
                afterI2(ILT); afterI2(I1); afterI1(KX); 
                afterI1(ILT); afterI1(I0); afterI0(KX);
        }
        while (--i != 0);
        
        Block::Put(xorBlock, outBlock)(a)(d)(b)(e);
}

NAMESPACE_END

---