aes_keyschedule.c

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/* aes_keyschedule.c */
/*
 This file is part of the AVR-Crypto-Lib.
 Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stdint.h>
#include "aes.h"
#include "aes_keyschedule.h"
#include "aes_sbox.h"
#include <string.h>
#include <platform/romem.h>
 
static
void aes_rotword(void *a)
{
    uint8_t t;
    t = ((uint8_t*) a)[0];
    ((uint8_t*) a)[0] = ((uint8_t*) a)[1];
    ((uint8_t*) a)[1] = ((uint8_t*) a)[2];
    ((uint8_t*) a)[2] = ((uint8_t*) a)[3];
    ((uint8_t*) a)[3] = t;
}
 
#define aes_rc_T_p     ROMEM_TABLE_P(rc_tab)
 
const uint8_t rc_tab[] ROMEM = { 0x01, 0x02, 0x04, 0x08,
        0x10, 0x20, 0x40, 0x80,
        0x1b, 0x36 };
 
void aes_init(const void *key, uint16_t keysize_b, aes_genctx_t *ctx)
{
    uint8_t hi, i, nk, next_nk;
    uint8_t rc = 0;
    union {
        uint32_t v32;
        uint8_t v8[4];
    } tmp;
    nk = keysize_b >> 5; /* 4, 6, 8 */
    hi = 4 * (nk + 6 + 1);
    memcpy(ctx, key, keysize_b / 8);
    next_nk = nk;
    for (i = nk; i < hi; ++i) {
        tmp.v32 = ((uint32_t*)(void *)(ctx->key[0].ks))[i - 1];
        if (i != next_nk) {
            if (nk == 8 && i % 8 == 4) {
                tmp.v8[0] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[0]);
                tmp.v8[1] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[1]);
                tmp.v8[2] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[2]);
                tmp.v8[3] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[3]);
            }
        } else {
            next_nk += nk;
            aes_rotword(&(tmp.v32));
            tmp.v8[0] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[0]);
            tmp.v8[1] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[1]);
            tmp.v8[2] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[2]);
            tmp.v8[3] = ROMEM_READ_BYTE(aes_sbox_T_p + tmp.v8[3]);
            tmp.v8[0] ^= ROMEM_READ_BYTE(aes_rc_T_p + rc);
            rc++;
        }
        ((uint32_t*)(void *)(ctx->key[0].ks))[i] = 
            ((uint32_t*)(void *)(ctx->key[0].ks))[i - nk] ^ tmp.v32;
    }
}
 
void aes128_init(const void *key, aes128_ctx_t *ctx)
{
    aes_init(key, 128, (aes_genctx_t*) ctx);
}
 
void aes192_init(const void *key, aes192_ctx_t *ctx)
{
    aes_init(key, 192, (aes_genctx_t*) ctx);
}
 
void aes256_init(const void *key, aes256_ctx_t *ctx)
{
    aes_init(key, 256, (aes_genctx_t*) ctx);
}