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blowfish.cpp

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

#include "pch.h"
#include "blowfish.h"

NAMESPACE_BEGIN(CryptoPP)

Blowfish::Blowfish(const byte *key_string, unsigned int keylength, CipherDir dir)
        : pbox(ROUNDS+2), sbox(4*256)
{
        assert(keylength == KeyLength(keylength));

        unsigned i, j=0, k;
        word32 data, dspace[2] = {0, 0};

        memcpy(pbox, p_init, sizeof(p_init));
        memcpy(sbox, s_init, sizeof(s_init));

        // Xor key string into encryption key vector
        for (i=0 ; i<ROUNDS+2 ; ++i)
        {
                data = 0 ;
                for (k=0 ; k<4 ; ++k )
                        data = (data << 8) | key_string[j++ % keylength];
                pbox[i] ^= data;
        }

        crypt_block(dspace, pbox);

        for (i=0; i<ROUNDS; i+=2)
                crypt_block(pbox+i, pbox+i+2);

        crypt_block(pbox+ROUNDS, sbox);

        for (i=0; i<4*256-2; i+=2)
                crypt_block(sbox+i, sbox+i+2);

        if (dir==DECRYPTION)
                for (i=0; i<(ROUNDS+2)/2; i++)
                        std::swap(pbox[i], pbox[ROUNDS+1-i]);
}

// this version is only used to make pbox and sbox
void Blowfish::crypt_block(const word32 in[2], word32 out[2]) const
{
        word32 left = in[0];
        word32 right = in[1];

        const word32 *const s=sbox;
        const word32 *p=pbox;

        left ^= p[0];

        for (unsigned i=0; i<ROUNDS/2; i++)
        {
                right ^= (((s[GETBYTE(left,3)] + s[256+GETBYTE(left,2)])
                          ^ s[2*256+GETBYTE(left,1)]) + s[3*256+GETBYTE(left,0)])
                          ^ p[2*i+1];

                left ^= (((s[GETBYTE(right,3)] + s[256+GETBYTE(right,2)])
                         ^ s[2*256+GETBYTE(right,1)]) + s[3*256+GETBYTE(right,0)])
                         ^ p[2*i+2];
        }

        right ^= p[ROUNDS+1];

        out[0] = right;
        out[1] = left;
}

void Blowfish::ProcessBlock(const byte *in, byte *out) const
{
        word32 left, right;
        GetBlockBigEndian(in, left, right);

        const word32 *const s=sbox;
        const word32 *p=pbox;

        left ^= p[0];

        for (unsigned i=0; i<ROUNDS/2; i++)
        {
                right ^= (((s[GETBYTE(left,3)] + s[256+GETBYTE(left,2)])
                          ^ s[2*256+GETBYTE(left,1)]) + s[3*256+GETBYTE(left,0)])
                          ^ p[2*i+1];

                left ^= (((s[GETBYTE(right,3)] + s[256+GETBYTE(right,2)])
                         ^ s[2*256+GETBYTE(right,1)]) + s[3*256+GETBYTE(right,0)])
                         ^ p[2*i+2];
        }

        right ^= p[ROUNDS+1];

        PutBlockBigEndian(out, right, left);
}

NAMESPACE_END

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