X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/417f4ae12711f28d8b27dcd29786a1cc9300aaad..bd46dec63beb7414ce26ec0517c06bf79f676b6d:/armsrc/crapto1.c
diff --git a/armsrc/crapto1.c b/armsrc/crapto1.c
index 4b4e240e..e2058651 100644
--- a/armsrc/crapto1.c
+++ b/armsrc/crapto1.c
@@ -15,7 +15,7 @@
Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, US$
- Copyright (C) 2008-2008 bla <blapost@gmail.com>
+ Copyright (C) 2008-2014 bla <blapost@gmail.com>
*/
#include "crapto1.h"
#include <stdlib.h>
@@ -24,9 +24,9 @@
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);
+ uint32_t i;
+ for(i = 0; i < 1 << 20; ++i)
+ filterlut[i] = filter(i);
}
#define filter(x) (filterlut[(x) & 0xfffff])
#endif
@@ -85,7 +85,8 @@ update_contribution(uint32_t *item, const uint32_t mask1, const uint32_t mask2)
/** 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)
+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)
@@ -183,6 +184,7 @@ struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)
uint32_t *even_head = 0, *even_tail = 0, eks = 0;
int i;
+ // split the keystream into an odd and even part
for(i = 31; i >= 0; i -= 2)
oks = oks << 1 | BEBIT(ks2, i);
for(i = 30; i >= 0; i -= 2)
@@ -199,6 +201,7 @@ struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)
statelist->odd = statelist->even = 0;
+ // initialize statelists: add all possible states which would result into the rightmost 2 bits of the keystream
for(i = 1 << 20; i >= 0; --i) {
if(filter(i) == (oks & 1))
*++odd_tail = i;
@@ -206,11 +209,15 @@ struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)
*++even_tail = i;
}
+ // extend the statelists. Look at the next 8 Bits of the keystream (4 Bit each odd and even):
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);
}
+ // the statelists now contain all states which could have generated the last 10 Bits of the keystream.
+ // 22 bits to go to recover 32 bits in total. From now on, we need to take the "in"
+ // parameter into account.
in = (in >> 16 & 0xff) | (in << 16) | (in & 0xff00);
recover(odd_head, odd_tail, oks,
even_head, even_tail, eks, 11, statelist, in << 1);
@@ -412,10 +419,11 @@ static uint16_t *dist = 0;
int nonce_distance(uint32_t from, uint32_t to)
{
uint16_t x, i;
- if(!dist) {
+ // generate distance lookup table
+ if (!dist) {
dist = malloc(2 << 16);
- if(!dist)
- return -1;
+ 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;
@@ -439,16 +447,14 @@ static uint32_t fastfwd[2][8] = {
* 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
*/
- // TO VERIFY
-uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd)
+uint32_t* lfsr_prefix_ks(uint8_t ks[8], int isodd)
{
uint32_t *candidates = malloc(4 << 10);
+ if(!candidates) return 0;
+
uint32_t c, entry;
int size = 0, i, 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];
@@ -467,9 +473,7 @@ uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd)
/** 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)
+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;
@@ -497,7 +501,6 @@ check_pfx_parity(uint32_t prefix, uint32_t rresp, uint8_t parities[8][8],
return sl + good;
}
-
/** lfsr_common_prefix
* Implentation of the common prefix attack.
* Requires the 28 bit constant prefix used as reader nonce (pfx)
@@ -507,8 +510,7 @@ check_pfx_parity(uint32_t prefix, uint32_t rresp, uint8_t parities[8][8],
* It returns a zero terminated list of possible cipher states after the
* tag nonce was fed in
*/
-struct Crypto1State*
-lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])
+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;
@@ -516,12 +518,11 @@ lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])
odd = lfsr_prefix_ks(ks, 1);
even = lfsr_prefix_ks(ks, 0);
- s = statelist = malloc((sizeof *statelist) << 20);
+ s = statelist = malloc((sizeof *statelist) << 21);
if(!s || !odd || !even) {
free(statelist);
- free(odd);
- free(even);
- return 0;
+ statelist = 0;
+ goto out;
}
for(o = odd; *o + 1; ++o)
@@ -533,9 +534,8 @@ lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])
}
s->odd = s->even = 0;
-
+out:
free(odd);
free(even);
-
return statelist;
-}
+}
\ No newline at end of file