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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
#include "tomcrypt.h"
#if defined(LTC_MDSA) || defined(LTC_MECC)
/**
Generate a random number N with given bitlength (note: MSB can be 0)
*/
int rand_bn_bits(void *N, int bits, prng_state *prng, int wprng)
{
int res, bytes;
unsigned char *buf, mask;
LTC_ARGCHK(N != NULL);
LTC_ARGCHK(bits > 1);
/* check PRNG */
if ((res = prng_is_valid(wprng)) != CRYPT_OK) return res;
bytes = (bits+7) >> 3;
mask = 0xff << (8 - bits % 8);
/* allocate buffer */
if ((buf = XCALLOC(1, bytes)) == NULL) return CRYPT_MEM;
/* generate random bytes */
if (prng_descriptor[wprng].read(buf, bytes, prng) != (unsigned long)bytes) {
res = CRYPT_ERROR_READPRNG;
goto cleanup;
}
/* mask bits */
buf[0] &= ~mask;
/* load value */
if ((res = mp_read_unsigned_bin(N, buf, bytes)) != CRYPT_OK) goto cleanup;
res = CRYPT_OK;
cleanup:
#ifdef LTC_CLEAN_STACK
zeromem(buf, bytes);
#endif
XFREE(buf);
return res;
}
/**
Generate a random number N in a range: 1 <= N < limit
*/
int rand_bn_upto(void *N, void *limit, prng_state *prng, int wprng)
{
int res, bits;
LTC_ARGCHK(N != NULL);
LTC_ARGCHK(limit != NULL);
bits = mp_count_bits(limit);
do {
res = rand_bn_bits(N, bits, prng, wprng);
if (res != CRYPT_OK) return res;
} while (mp_cmp_d(N, 0) != LTC_MP_GT || mp_cmp(N, limit) != LTC_MP_LT);
return CRYPT_OK;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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