mars.cpp

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

// includes IBM's key setup "tweak" proposed in August 1999 (http://www.research.ibm.com/security/key-setup.txt)

#include "pch.h"
#include "mars.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

void MARS::Base::UncheckedSetKey(const byte *userKey, unsigned int length, const NameValuePairs &)
{
        AssertValidKeyLength(length);

        // Initialize T[] with the key data
        FixedSizeSecBlock<word32, 15> T;
        GetUserKey(LITTLE_ENDIAN_ORDER, T.begin(), 15, userKey, length);
        T[length/4] = length/4;

        for (unsigned int j=0; j<4; j++)        // compute 10 words of K[] in each iteration
        {
                unsigned int i;
                // Do linear transformation
                for (i=0; i<15; i++)
                        T[i] = T[i] ^ rotlFixed(T[(i+8)%15] ^ T[(i+13)%15], 3) ^ (4*i+j);

                // Do four rounds of stirring
                for (unsigned int k=0; k<4; k++)
                        for (i=0; i<15; i++)
                           T[i] = rotlFixed(T[i] + Sbox[T[(i+14)%15]%512], 9);

                // Store next 10 key words into K[]
                for (i=0; i<10; i++)
                        m_k[10*j+i] = T[4*i%15];
        }

        // Modify multiplication key-words
        for(unsigned int i = 5; i < 37; i += 2)
        {
                word32 m, w = m_k[i] | 3;
                m = (~w ^ (w<<1)) & (~w ^ (w>>1)) & 0x7ffffffe;
                m &= m>>1; m &= m>>2; m &= m>>4;
                m |= m<<1; m |= m<<2; m |= m<<4;
                m &= 0x7ffffffc;
                w ^= rotlMod(Sbox[265 + (m_k[i] & 3)], m_k[i-1]) & m;
                m_k[i] = w;
        }
}

#define S(a)    Sbox[(a)&0x1ff]
#define S0(a)   Sbox[(a)&0xff]
#define S1(a)   Sbox[((a)&0xff) + 256]

typedef BlockGetAndPut<word32, LittleEndian> Block;

void MARS::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        unsigned int i;
        word32 a, b, c, d, l, m, r, t;
        const word32 *k = m_k;
        
        Block::Get(inBlock)(a)(b)(c)(d);

        a += k[0];      b += k[1];      c += k[2];      d += k[3];

        for (i=0; i<8; i++)
        {
                b = (b ^ S0(a)) + S1(a>>8);
                c += S0(a>>16);
                a = rotrFixed(a, 24);
                d ^= S1(a);
                a += (i%4==0) ? d : 0;
                a += (i%4==1) ? b : 0;
                t = a;  a = b;  b = c;  c = d;  d = t;
        }

        for (i=0; i<16; i++)
        {
                t = rotlFixed(a, 13);
                r = rotlFixed(t * k[2*i+5], 10);
                m = a + k[2*i+4];
                l = rotlMod((S(m) ^ rotrFixed(r, 5) ^ r), r);
                c += rotlMod(m, rotrFixed(r, 5));
                (i<8 ? b : d) += l;
                (i<8 ? d : b) ^= r;
                a = b;  b = c;  c = d;  d = t;
        }

        for (i=0; i<8; i++)
        {
                a -= (i%4==2) ? d : 0;
                a -= (i%4==3) ? b : 0;
                b ^= S1(a);
                c -= S0(a>>24);
                t = rotlFixed(a, 24);
                d = (d - S1(a>>16)) ^ S0(t);
                a = b;  b = c;  c = d;  d = t;
        }

        a -= k[36];     b -= k[37];     c -= k[38];     d -= k[39];

        Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
}

void MARS::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        unsigned int i;
        word32 a, b, c, d, l, m, r, t;
        const word32 *k = m_k;

        Block::Get(inBlock)(d)(c)(b)(a);
        
        d += k[36];     c += k[37];     b += k[38];     a += k[39];

        for (i=0; i<8; i++)
        {
                b = (b ^ S0(a)) + S1(a>>8);
                c += S0(a>>16);
                a = rotrFixed(a, 24);
                d ^= S1(a);
                a += (i%4==0) ? d : 0;
                a += (i%4==1) ? b : 0;
                t = a;  a = b;  b = c;  c = d;  d = t;
        }

        for (i=0; i<16; i++)
        {
                t = rotrFixed(a, 13);
                r = rotlFixed(a * k[35-2*i], 10);
                m = t + k[34-2*i];
                l = rotlMod((S(m) ^ rotrFixed(r, 5) ^ r), r);
                c -= rotlMod(m, rotrFixed(r, 5));
                (i<8 ? b : d) -= l;
                (i<8 ? d : b) ^= r;
                a = b;  b = c;  c = d;  d = t;
        }

        for (i=0; i<8; i++)
        {
                a -= (i%4==2) ? d : 0;
                a -= (i%4==3) ? b : 0;
                b ^= S1(a);
                c -= S0(a>>24);
                t = rotlFixed(a, 24);
                d = (d - S1(a>>16)) ^ S0(t);
                a = b;  b = c;  c = d;  d = t;
        }

        d -= k[0];      c -= k[1];      b -= k[2];      a -= k[3];

        Block::Put(xorBlock, outBlock)(d)(c)(b)(a);
}

NAMESPACE_END