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upgtools: fix bug in brute force search

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DES ignores the parity bit of each byte (making the 64-bit key really 56-bit),
but the current code skipped the parity bit of each half-byte, thus missing
some keys.

Change-Id: Ia523ebb944e458905b7de1742df151df22166150
This commit is contained in:
Amaury Pouly 2017-09-19 15:30:37 +02:00
parent 048aecd82a
commit 99cc8f8802
1 changed files with 8 additions and 6 deletions
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14
utils/nwztools/upgtools/keysig_search.c
View file

@ -266,11 +266,12 @@ static bool hex_rec(bool producer, struct hex_chunk_t *ch)
* significant bit of each byte is an (unused) parity bit. We thus only
* generate keys where the least significant bit is 0. */
int p = ch->pos++;
int step = (p % 2) ? 2 : 1; // skip significant bit at positions 1, 3, 5 and 7
if(ch->rem_digits > 0)
{
ch->rem_digits--;
/* NOTE (42) */
for(int i = '0'; i <= '9'; i += 2)
for(int i = '0'; i <= '9'; i += step)
{
ch->key[p] = i;
if(hex_rec(producer, ch))
@ -282,7 +283,7 @@ static bool hex_rec(bool producer, struct hex_chunk_t *ch)
{
ch->rem_letters--;
/* NOTE (42) */
for(int i = 'a'; i <= 'f'; i += 2)
for(int i = 'a'; i <= 'f'; i += step)
{
ch->key[p] = i;
if(hex_rec(producer, ch))
@ -290,7 +291,7 @@ static bool hex_rec(bool producer, struct hex_chunk_t *ch)
}
if(ch->upper_case)
{
for(int i = 'A'; i <= 'F'; i += 2)
for(int i = 'A'; i <= 'F'; i += step)
{
ch->key[p] = i;
if(hex_rec(producer, ch))
@ -379,7 +380,7 @@ static bool alnum_rec(bool producer, struct alnum_chunk_t *ch)
/* we list the first 5 pos in generator, and remaining 3 in workers */
if(producer && ch->pos == 4)
{
printf("yield(%.8s,%d)\n", ch->key, ch->pos);
//printf("yield(%.8s,%d)\n", ch->key, ch->pos);
return producer_yield(ch, sizeof(struct alnum_chunk_t));
}
/* filled the key ? */
@ -392,14 +393,15 @@ static bool alnum_rec(bool producer, struct alnum_chunk_t *ch)
* generate keys where the least significant bit is 0. */
int p = ch->pos++;
/* NOTE (42) */
for(int i = '0'; i <= '9'; i += 2)
int step = (p % 2) ? 2 : 1; // skip significant bit at positions 1, 3, 5 and 7
for(int i = '0'; i <= '9'; i += step)
{
ch->key[p] = i;
if(alnum_rec(producer, ch))
return true;
}
/* NOTE (42) */
for(int i = 'a'; i <= 'z'; i += 2)
for(int i = 'a'; i <= 'z'; i += step)
{
ch->key[p] = i;
if(alnum_rec(producer, ch))