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POLY: cleanup pb_starmultiply()

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* avoid side effects
* use MP_DIV instead of MP_MOD
* move mp_modulus initialization to outer scope
This commit is contained in:
hasufell 2014-04-17 17:36:57 +02:00
parent 03a05f2dad
commit cc82e4e3bd
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GPG Key ID: 220CD1C5BDEED020
2 changed files with 24 additions and 8 deletions
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24
src/poly.c
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@ -178,6 +178,17 @@ void pb_starmultiply(pb_poly *a,
ntru_context *ctx, ntru_context *ctx,
unsigned int modulus) unsigned int modulus)
{ {
pb_poly *a_tmp;
mp_int mp_modulus;
init_integer(&mp_modulus);
mp_set_int(&mp_modulus, (unsigned long)(modulus));
/* avoid side effects */
a_tmp = build_polynom(NULL, ctx->N, ctx);
PB_COPY(a, a_tmp);
erase_polynom(c, ctx->N);
for (int k = ctx->N - 1; k >= 0; k--) { for (int k = ctx->N - 1; k >= 0; k--) {
int j; int j;
j = k + 1; j = k + 1;
@ -185,26 +196,23 @@ void pb_starmultiply(pb_poly *a,
for (int i = ctx->N - 1; i >= 0; i--) { for (int i = ctx->N - 1; i >= 0; i--) {
if (j == (int)(ctx->N)) if (j == (int)(ctx->N))
j = 0; j = 0;
if (mp_cmp_d(&(a->terms[i]), 0) != MP_EQ && if (mp_cmp_d(&(a_tmp->terms[i]), 0) != MP_EQ &&
mp_cmp_d(&(b->terms[j]), 0) != MP_EQ) { mp_cmp_d(&(b->terms[j]), 0) != MP_EQ) {
int result;
mp_int mp_modulus;
mp_int mp_tmp; mp_int mp_tmp;
init_integer(&mp_tmp); init_integer(&mp_tmp);
init_integer(&mp_modulus);
mp_set_int(&mp_modulus, (unsigned long)(modulus));
MP_MUL(&(a->terms[i]), &(b->terms[j]), &mp_tmp); MP_MUL(&(a_tmp->terms[i]), &(b->terms[j]), &mp_tmp);
MP_ADD(&(c->terms[k]), &mp_tmp, &(c->terms[k])); MP_ADD(&(c->terms[k]), &mp_tmp, &(c->terms[k]));
MP_MOD(&(c->terms[k]), &mp_modulus, &(c->terms[k])); MP_DIV(&(c->terms[k]), &mp_modulus, NULL, &(c->terms[k]));
mp_clear(&mp_modulus);
mp_clear(&mp_tmp); mp_clear(&mp_tmp);
} }
j++; j++;
} }
} }
mp_clear(&mp_modulus);
delete_polynom(a_tmp);
} }
/** /**

8
src/poly.h
View File

@ -38,6 +38,14 @@
mp_error_to_string(result)); \ mp_error_to_string(result)); \
} }
#define MP_DIV(...) \
{ \
int result; \
if ((result = mp_div(__VA_ARGS__)) != MP_OKAY) \
NTRU_ABORT("Error dividing terms. %s", \
mp_error_to_string(result)); \
}
#define MP_ADD(...) \ #define MP_ADD(...) \
{ \ { \
int result; \ int result; \