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/*
---------------------------------------------------------------------------
Copyright (c) 2003, Dr Brian Gladman < >, Worcester, UK.
All rights reserved.
LICENSE TERMS
The free distribution and use of this software in both source and binary
form is allowed (with or without changes) provided that:
1. distributions of this source code include the above copyright
notice, this list of conditions and the following disclaimer;
2. distributions in binary form include the above copyright
notice, this list of conditions and the following disclaimer
in the documentation and/or other associated materials;
3. the copyright holder's name is not used to endorse products
built using this software without specific written permission.
ALTERNATIVELY, provided that this notice is retained in full, this product
may be distributed under the terms of the GNU General Public License (GPL),
in which case the provisions of the GPL apply INSTEAD OF those given above.
DISCLAIMER
This software is provided 'as is' with no explicit or implied warranties
in respect of its properties, including, but not limited to, correctness
and/or fitness for purpose.
---------------------------------------------------------------------------
Issue Date: 26/08/2003
*/
#define DO_TABLES
#include "aesopt.h"
#if defined(FIXED_TABLES)
/* implemented in case of wrong call for fixed tables */
void gen_tabs(void)
{
}
#else /* dynamic table generation */
#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 aes_08t hibit(const aes_32t x)
{ aes_08t r = (aes_08t)((x >> 1) | (x >> 2));
r |= (r >> 2);
r |= (r >> 4);
return (r + 1) >> 1;
}
/* return the inverse of the finite field element x */
static aes_08t fi(const aes_08t x)
{ aes_08t 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);
}
}
}
#endif
/* The forward and inverse affine transformations used in the S-box */
#define fwd_affine(x) \
(w = (aes_32t)x, w ^= (w<<1)^(w<<2)^(w<<3)^(w<<4), 0x63^(aes_08t)(w^(w>>8)))
#define inv_affine(x) \
(w = (aes_32t)x, w = (w<<1)^(w<<3)^(w<<6), 0x05^(aes_08t)(w^(w>>8)))
static int init = 0;
void gen_tabs(void)
{ aes_32t i, w;
#if defined(FF_TABLES)
aes_08t pow[512], log[256];
if(init) return;
/* 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] = (aes_08t)w;
pow[i + 255] = (aes_08t)w;
log[w] = (aes_08t)i++;
w ^= (w << 1) ^ (w & 0x80 ? WPOLY : 0);
}
while (w != 1);
#else
if(init) return;
#endif
for(i = 0, w = 1; i < RC_LENGTH; ++i)
{
t_set(r,c)[i] = bytes2word(w, 0, 0, 0);
w = f2(w);
}
for(i = 0; i < 256; ++i)
{ aes_08t b;
b = fwd_affine(fi((aes_08t)i));
w = bytes2word(f2(b), b, b, f3(b));
#ifdef SBX_SET
t_set(s,box)[i] = b;
#endif
#ifdef FT1_SET /* tables for a normal encryption round */
t_set(f,n)[i] = w;
#endif
#ifdef FT4_SET
t_set(f,n)[0][i] = w;
t_set(f,n)[1][i] = upr(w,1);
t_set(f,n)[2][i] = upr(w,2);
t_set(f,n)[3][i] = upr(w,3);
#endif
w = bytes2word(b, 0, 0, 0);
#ifdef FL1_SET /* tables for last encryption round (may also */
t_set(f,l)[i] = w; /* be used in the key schedule) */
#endif
#ifdef FL4_SET
t_set(f,l)[0][i] = w;
t_set(f,l)[1][i] = upr(w,1);
t_set(f,l)[2][i] = upr(w,2);
t_set(f,l)[3][i] = upr(w,3);
#endif
#ifdef LS1_SET /* table for key schedule if t_set(f,l) above is */
t_set(l,s)[i] = w; /* not of the required form */
#endif
#ifdef LS4_SET
t_set(l,s)[0][i] = w;
t_set(l,s)[1][i] = upr(w,1);
t_set(l,s)[2][i] = upr(w,2);
t_set(l,s)[3][i] = upr(w,3);
#endif
b = fi(inv_affine((aes_08t)i));
w = bytes2word(fe(b), f9(b), fd(b), fb(b));
#ifdef IM1_SET /* tables for the inverse mix column operation */
t_set(i,m)[b] = w;
#endif
#ifdef IM4_SET
t_set(i,m)[0][b] = w;
t_set(i,m)[1][b] = upr(w,1);
t_set(i,m)[2][b] = upr(w,2);
t_set(i,m)[3][b] = upr(w,3);
#endif
#ifdef ISB_SET
t_set(i,box)[i] = b;
#endif
#ifdef IT1_SET /* tables for a normal decryption round */
t_set(i,n)[i] = w;
#endif
#ifdef IT4_SET
t_set(i,n)[0][i] = w;
t_set(i,n)[1][i] = upr(w,1);
t_set(i,n)[2][i] = upr(w,2);
t_set(i,n)[3][i] = upr(w,3);
#endif
w = bytes2word(b, 0, 0, 0);
#ifdef IL1_SET /* tables for last decryption round */
t_set(i,l)[i] = w;
#endif
#ifdef IL4_SET
t_set(i,l)[0][i] = w;
t_set(i,l)[1][i] = upr(w,1);
t_set(i,l)[2][i] = upr(w,2);
t_set(i,l)[3][i] = upr(w,3);
#endif
}
init = 1;
}
#endif
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