63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
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/* LibTomPoly, Polynomial Basis Math -- Tom St Denis
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*
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* LibTomPoly is a public domain library that provides
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* polynomial basis arithmetic support. It relies on
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* LibTomMath for large integer support.
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*
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* This library is free for all purposes without any
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* express guarantee that it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://poly.libtomcrypt.org
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*/
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#include <tompoly.h>
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int pb_mul(pb_poly *a, pb_poly *b, pb_poly *c)
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{
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int err, x, y;
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pb_poly tmp;
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mp_int tmp2;
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/* make temp */
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if ((err = pb_init_size(&tmp, &(c->characteristic), a->used + b->used)) != MP_OKAY) {
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return err;
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}
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if ((err = mp_init(&tmp2)) != MP_OKAY) {
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goto __TMP;
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}
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/* multiply the terms */
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for (x = 0; x < a->used; x++) {
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for (y = 0; y < b->used; y++) {
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if ((err = mp_mul(&(a->terms[x]), &(b->terms[y]), &tmp2)) != MP_OKAY) {
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goto __TMP2;
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}
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if ((err = mp_add(&tmp2, &(tmp.terms[x+y]), &(tmp.terms[x+y]))) != MP_OKAY) {
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goto __TMP2;
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}
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}
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}
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/* now reduce the terms as required */
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if (mp_iszero(&(c->characteristic)) == MP_NO) {
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for (x = 0; x < (a->used + b->used); x++) {
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if ((err = mp_mod(&(tmp.terms[x]), &(c->characteristic), &(tmp.terms[x]))) != MP_OKAY) {
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goto __TMP2;
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}
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}
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}
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/* set digit count */
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tmp.used = a->used + b->used;
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pb_clamp(&tmp);
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/* exchange tmp and c */
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pb_exch(&tmp, c);
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err = MP_OKAY;
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__TMP2: mp_clear(&tmp2);
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__TMP : pb_clear(&tmp);
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return err;
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}
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