/* * mpbrnd_w * generates a random number in the range 1 < r < b-1 * need workspace of (size) words */ void mpbrnd_w(const mpbarrett* b, randomGeneratorContext* rc, mpw* result, mpw* wksp) { size_t msz = mpmszcnt(b->size, b->modl); mpcopy(b->size, wksp, b->modl); mpsubw(b->size, wksp, 1); do { rc->rng->next(rc->param, (byte*) result, MP_WORDS_TO_BYTES(b->size)); result[0] &= (MP_ALLMASK >> msz); while (mpge(b->size, result, wksp)) mpsub(b->size, result, wksp); } while (mpleone(b->size, result)); }
/* * needs workspace of (size*2) words */ static void mpprndbits(mpbarrett* p, size_t bits, size_t lsbset, const mpnumber* min, const mpnumber* max, randomGeneratorContext* rc, mpw* wksp) { register size_t size = p->size; register size_t msbclr = MP_WORDS_TO_BITS(size) - bits; /* assume that mpbits(max) == bits */ /* calculate k=max-min; generate q such that 0 <= q <= k; then set p = q + min */ /* for the second step, set the appropriate number of bits */ if (max) { mpsetx(size, wksp, max->size, max->data); } else { mpfill(size, wksp, MP_ALLMASK); wksp[0] &= (MP_ALLMASK >> msbclr); } if (min) { mpsetx(size, wksp+size, min->size, min->data); } else { mpzero(size, wksp+size); wksp[size] |= (MP_MSBMASK >> msbclr); } mpsub(size, wksp, wksp+size); rc->rng->next(rc->param, (byte*) p->modl, MP_WORDS_TO_BYTES(size)); p->modl[0] &= (MP_ALLMASK >> msbclr); while (mpgt(size, p->modl, wksp)) mpsub(size, p->modl, wksp); mpadd(size, p->modl, wksp+size); if (lsbset) p->modl[size-1] |= (MP_ALLMASK >> (MP_WBITS - lsbset)); }