revert field on/off in hf 14a reader

[proxmark3-svn] / common / crapto1 / crypto1.c

/*  crypto1.c

        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 2
        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, write to the Free Software
        Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
        MA  02110-1301, US

        Copyright (C) 2008-2008 bla <blapost@gmail.com>
*/
#include "crapto1.h"

#include <stdlib.h>
#include "parity.h"

#define SWAPENDIAN(x)\
        (x = (x >> 8 & 0xff00ff) | (x & 0xff00ff) << 8, x = x >> 16 | x << 16)

#if defined(__arm__) && !defined(__linux__) && !defined(_WIN32) && !defined(__APPLE__)          // bare metal ARM Proxmark lacks malloc()/free()
void crypto1_create(struct Crypto1State *s, uint64_t key)
{
        int i;

        for(i = 47;s && i > 0; i -= 2) {
                s->odd  = s->odd  << 1 | BIT(key, (i - 1) ^ 7);
                s->even = s->even << 1 | BIT(key, i ^ 7);
        }
        return;
}
void crypto1_destroy(struct Crypto1State *state)
{
        state->odd = 0;
        state->even = 0;
}
#else
struct Crypto1State * crypto1_create(uint64_t key)
{
        struct Crypto1State *s = malloc(sizeof(*s));
        int i;

        for(i = 47;s && i > 0; i -= 2) {
                s->odd  = s->odd  << 1 | BIT(key, (i - 1) ^ 7);
                s->even = s->even << 1 | BIT(key, i ^ 7);
        }
        return s;
}
void crypto1_destroy(struct Crypto1State *state)
{
        free(state);
}
#endif
void crypto1_get_lfsr(struct Crypto1State *state, uint64_t *lfsr)
{
        int i;
        for(*lfsr = 0, i = 23; i >= 0; --i) {
                *lfsr = *lfsr << 1 | BIT(state->odd, i ^ 3);
                *lfsr = *lfsr << 1 | BIT(state->even, i ^ 3);
        }
}
uint8_t crypto1_bit(struct Crypto1State *s, uint8_t in, int is_encrypted)
{
        uint32_t feedin, t;
        uint8_t ret = filter(s->odd);

        feedin  = ret & !!is_encrypted;
        feedin ^= !!in;
        feedin ^= LF_POLY_ODD & s->odd;
        feedin ^= LF_POLY_EVEN & s->even;
        s->even = s->even << 1 | evenparity32(feedin);

        t = s->odd, s->odd = s->even, s->even = t;

        return ret;
}
uint8_t crypto1_byte(struct Crypto1State *s, uint8_t in, int is_encrypted)
{
        uint8_t i, ret = 0;

        for (i = 0; i < 8; ++i)
                ret |= crypto1_bit(s, BIT(in, i), is_encrypted) << i;

        return ret;
}
uint32_t crypto1_word(struct Crypto1State *s, uint32_t in, int is_encrypted)
{
        uint32_t i, ret = 0;

        for (i = 0; i < 32; ++i)
                ret |= crypto1_bit(s, BEBIT(in, i), is_encrypted) << (i ^ 24);

        return ret;
}

/* prng_successor
 * helper used to obscure the keystream during authentication
 */
uint32_t prng_successor(uint32_t x, uint32_t n)
{
        SWAPENDIAN(x);
        while(n--)
                x = x >> 1 | (x >> 16 ^ x >> 18 ^ x >> 19 ^ x >> 21) << 31;

        return SWAPENDIAN(x);
}