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