serpent.cpp

// serpent.cpp - originally written and placed in the public domain by Wei Dai
 
#include "pch.h"
 
#include "serpent.h"
#include "secblock.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 = rotlConstant<11>(k0[i] ^ k0[(i + 3) % 8] ^ k0[(i + 5) % 8] ^ t ^ 0x9e3779b9 ^ i);
    for (i = 8; i < 4*(rounds+1); ++i)
        k[i] = t = rotlConstant<11>(k[i-8] ^ k[i-5] ^ k[i-3] ^ t ^ 0x9e3779b9 ^ i);
    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=0;
 
    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