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fix ecc sign/hash truncation with odd bit sizes when hash length is longer than key size

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This commit is contained in:
toddouska
2013-07-25 15:59:09 -07:00
parent 55401c13dd
commit 505b1a8a67
5 changed files with 105 additions and 63 deletions
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63
ctaocrypt/src/integer.c
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@@ -328,8 +328,7 @@ bn_reverse (unsigned char *s, int len)
remainder in d) */
int mp_div_2d (mp_int * a, int b, mp_int * c, mp_int * d)
{
mp_digit D, r, rr;
int x, res;
int D, res;
mp_int t;
@@ -366,33 +365,9 @@ int mp_div_2d (mp_int * a, int b, mp_int * c, mp_int * d)
}
/* shift any bit count < DIGIT_BIT */
D = (mp_digit) (b % DIGIT_BIT);
D = (b % DIGIT_BIT);
if (D != 0) {
register mp_digit *tmpc, mask, shift;
/* mask */
mask = (((mp_digit)1) << D) - 1;
/* shift for lsb */
shift = DIGIT_BIT - D;
/* alias */
tmpc = c->dp + (c->used - 1);
/* carry */
r = 0;
for (x = c->used - 1; x >= 0; x--) {
/* get the lower bits of this word in a temp */
rr = *tmpc & mask;
/* shift the current word and mix in the carry bits from the previous
word */
*tmpc = (*tmpc >> D) | (r << shift);
--tmpc;
/* set the carry to the carry bits of the current word found above */
r = rr;
}
mp_rshb(c, D);
}
mp_clamp (c);
if (d != NULL) {
@@ -457,6 +432,38 @@ mp_exch (mp_int * a, mp_int * b)
}
/* shift right a certain number of bits */
void mp_rshb (mp_int *c, int x)
{
register mp_digit *tmpc, mask, shift;
mp_digit r, rr;
mp_digit D = x;
/* mask */
mask = (((mp_digit)1) << D) - 1;
/* shift for lsb */
shift = DIGIT_BIT - D;
/* alias */
tmpc = c->dp + (c->used - 1);
/* carry */
r = 0;
for (x = c->used - 1; x >= 0; x--) {
/* get the lower bits of this word in a temp */
rr = *tmpc & mask;
/* shift the current word and mix in the carry bits from previous word */
*tmpc = (*tmpc >> D) | (r << shift);
--tmpc;
/* set the carry to the carry bits of the current word found above */
r = rr;
}
}
/* shift right a certain amount of digits */
void mp_rshd (mp_int * a, int b)
{