aestab.c

aesutil是一个小型的库和命令行程序

const uint32_t im_tab[256] = { mm_data(v0) };
#endif
#ifdef  IM4_SET
const uint32_t im_tab[4][256] = 
    { {  mm_data(v0) }, {  mm_data(v1) }, {  mm_data(v2) }, {  mm_data(v3) } };
#endif

#else   /* dynamic table generation */

uint8_t tab_init = 0;

#define const

uint32_t  rcon_tab[RC_LENGTH];

#ifdef  SBX_SET
uint8_t s_box[256];
#endif
#ifdef  ISB_SET
uint8_t inv_s_box[256];
#endif

#ifdef  FT1_SET
uint32_t ft_tab[256];
#endif
#ifdef  FT4_SET
uint32_t ft_tab[4][256];
#endif

#ifdef  FL1_SET
uint32_t fl_tab[256];
#endif
#ifdef  FL4_SET
uint32_t fl_tab[4][256];
#endif

#ifdef  IT1_SET
uint32_t it_tab[256];
#endif
#ifdef  IT4_SET
uint32_t it_tab[4][256];
#endif

#ifdef  IL1_SET
uint32_t il_tab[256];
#endif
#ifdef  IL4_SET
uint32_t il_tab[4][256];
#endif

#ifdef  LS1_SET
uint32_t ls_tab[256];
#endif
#ifdef  LS4_SET
uint32_t ls_tab[4][256];
#endif

#ifdef  IM1_SET
uint32_t im_tab[256];
#endif
#ifdef  IM4_SET
uint32_t im_tab[4][256];
#endif

#if !defined(FF_TABLES)

/*  Generate the tables for the dynamic table option

    It will generally be sensible to use tables to compute finite 
    field multiplies and inverses but where memory is scarse this 
    code might sometimes be better. But it only has effect during
    initialisation so its pretty unimportant in overall terms.
*/

/*  return 2 ^ (n - 1) where n is the bit number of the highest bit
    set in x with x in the range 1 < x < 0x00000200.   This form is
    used so that locals within fi can be bytes rather than words
*/

static uint8_t hibit(const uint32_t x)
{   uint8_t r = (uint8_t)((x >> 1) | (x >> 2));
    
    r |= (r >> 2);
    r |= (r >> 4);
    return (r + 1) >> 1;
}

/* return the inverse of the finite field element x */

static uint8_t fi(const uint8_t x)
{   uint8_t p1 = x, p2 = BPOLY, n1 = hibit(x), n2 = 0x80, v1 = 1, v2 = 0;

    if(x < 2) return x;

    for(;;)
    {
        if(!n1) return v1;

        while(n2 >= n1)
        {   
            n2 /= n1; p2 ^= p1 * n2; v2 ^= v1 * n2; n2 = hibit(p2);
        }
        
        if(!n2) return v2;

        while(n1 >= n2)
        {   
            n1 /= n2; p1 ^= p2 * n1; v1 ^= v2 * n1; n1 = hibit(p1);
        }
    }
}

#else

/* define the finite field multiplies required for Rijndael */

#define f2(x) ((x) ? pow[log[x] + 0x19] : 0)
#define f3(x) ((x) ? pow[log[x] + 0x01] : 0)
#define f9(x) ((x) ? pow[log[x] + 0xc7] : 0)
#define fb(x) ((x) ? pow[log[x] + 0x68] : 0)
#define fd(x) ((x) ? pow[log[x] + 0xee] : 0)
#define fe(x) ((x) ? pow[log[x] + 0xdf] : 0)
#define fi(x) ((x) ?   pow[255 - log[x]]: 0)

#endif

/* The forward and inverse affine transformations used in the S-box */

#define fwd_affine(x) \
    (w = (uint32_t)x, w ^= (w<<1)^(w<<2)^(w<<3)^(w<<4), 0x63^(uint8_t)(w^(w>>8)))

#define inv_affine(x) \
    (w = (uint32_t)x, w = (w<<1)^(w<<3)^(w<<6), 0x05^(uint8_t)(w^(w>>8)))

void gen_tabs(void)
{   uint32_t  i, w;

#if defined(FF_TABLES)

    uint8_t  pow[512], log[256];

    /*  log and power tables for GF(2^8) finite field with
        WPOLY as modular polynomial - the simplest primitive
        root is 0x03, used here to generate the tables
    */

    i = 0; w = 1; 
    do
    {   
        pow[i] = (uint8_t)w;
        pow[i + 255] = (uint8_t)w;
        log[w] = (uint8_t)i++;
        w ^=  (w << 1) ^ (w & 0x80 ? WPOLY : 0);
    }
    while (w != 1);

#endif

    for(i = 0, w = 1; i < RC_LENGTH; ++i)
    {
        rcon_tab[i] = bytes2word(w, 0, 0, 0);
        w = f2(w);
    }

    for(i = 0; i < 256; ++i)
    {   uint8_t    b;

        b = fwd_affine(fi((uint8_t)i));
        w = bytes2word(f2(b), b, b, f3(b));

#ifdef  SBX_SET
        s_box[i] = b;
#endif

#ifdef  FT1_SET                 /* tables for a normal encryption round */
        ft_tab[i] = w;
#endif
#ifdef  FT4_SET
        ft_tab[0][i] = w;
        ft_tab[1][i] = upr(w,1);
        ft_tab[2][i] = upr(w,2);
        ft_tab[3][i] = upr(w,3);
#endif
        w = bytes2word(b, 0, 0, 0);

#ifdef  FL1_SET                 /* tables for last encryption round (may also   */
        fl_tab[i] = w;          /* be used in the key schedule)                 */
#endif
#ifdef  FL4_SET
        fl_tab[0][i] = w;
        fl_tab[1][i] = upr(w,1);
        fl_tab[2][i] = upr(w,2);
        fl_tab[3][i] = upr(w,3);
#endif

#ifdef  LS1_SET                 /* table for key schedule if fl_tab above is    */
        ls_tab[i] = w;          /* not of the required form                     */
#endif
#ifdef  LS4_SET
        ls_tab[0][i] = w;
        ls_tab[1][i] = upr(w,1);
        ls_tab[2][i] = upr(w,2);
        ls_tab[3][i] = upr(w,3);
#endif

        b = fi(inv_affine((uint8_t)i));
        w = bytes2word(fe(b), f9(b), fd(b), fb(b));

#ifdef  IM1_SET                 /* tables for the inverse mix column operation  */
        im_tab[b] = w;
#endif
#ifdef  IM4_SET
        im_tab[0][b] = w;
        im_tab[1][b] = upr(w,1);
        im_tab[2][b] = upr(w,2);
        im_tab[3][b] = upr(w,3);
#endif

#ifdef  ISB_SET
        inv_s_box[i] = b;
#endif
#ifdef  IT1_SET                 /* tables for a normal decryption round */
        it_tab[i] = w;
#endif
#ifdef  IT4_SET
        it_tab[0][i] = w;
        it_tab[1][i] = upr(w,1);
        it_tab[2][i] = upr(w,2);
        it_tab[3][i] = upr(w,3);
#endif
        w = bytes2word(b, 0, 0, 0);
#ifdef  IL1_SET                 /* tables for last decryption round */
        il_tab[i] = w;
#endif
#ifdef  IL4_SET
        il_tab[0][i] = w;
        il_tab[1][i] = upr(w,1);
        il_tab[2][i] = upr(w,2);
        il_tab[3][i] = upr(w,3);
#endif
    }

    tab_init = 1;
}

#endif