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annotate libtomcrypt/src/math/rand_bn.c @ 1734:73646de50f13 DROPBEAR_2020.80

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version 2020.80
author Matt Johnston <matt@ucc.asn.au>
date Fri, 26 Jun 2020 21:45:59 +0800
parents e9dba7abd939
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1471
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 #if defined(LTC_MDSA) || defined(LTC_MECC)
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12 /**
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13 Generate a random number N with given bitlength (note: MSB can be 0)
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14 */
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15
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16 int rand_bn_bits(void *N, int bits, prng_state *prng, int wprng)
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17 {
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18 int res, bytes;
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19 unsigned char *buf, mask;
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20
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21 LTC_ARGCHK(N != NULL);
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22 LTC_ARGCHK(bits > 1);
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23
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24 /* check PRNG */
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25 if ((res = prng_is_valid(wprng)) != CRYPT_OK) return res;
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26
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27 bytes = (bits+7) >> 3;
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28 mask = 0xff << (8 - bits % 8);
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29
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30 /* allocate buffer */
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31 if ((buf = XCALLOC(1, bytes)) == NULL) return CRYPT_MEM;
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32
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33 /* generate random bytes */
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34 if (prng_descriptor[wprng].read(buf, bytes, prng) != (unsigned long)bytes) {
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35 res = CRYPT_ERROR_READPRNG;
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36 goto cleanup;
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37 }
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38 /* mask bits */
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39 buf[0] &= ~mask;
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40 /* load value */
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41 if ((res = mp_read_unsigned_bin(N, buf, bytes)) != CRYPT_OK) goto cleanup;
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42
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43 res = CRYPT_OK;
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44
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45 cleanup:
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46 #ifdef LTC_CLEAN_STACK
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47 zeromem(buf, bytes);
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48 #endif
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49 XFREE(buf);
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50 return res;
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51 }
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52
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53 /**
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54 Generate a random number N in a range: 1 <= N < limit
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55 */
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56 int rand_bn_upto(void *N, void *limit, prng_state *prng, int wprng)
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57 {
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58 int res, bits;
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59
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60 LTC_ARGCHK(N != NULL);
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61 LTC_ARGCHK(limit != NULL);
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62
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63 bits = mp_count_bits(limit);
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64 do {
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65 res = rand_bn_bits(N, bits, prng, wprng);
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66 if (res != CRYPT_OK) return res;
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67 } while (mp_cmp_d(N, 0) != LTC_MP_GT || mp_cmp(N, limit) != LTC_MP_LT);
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68
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69 return CRYPT_OK;
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70 }
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71 #endif
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72
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73 /* ref: $Format:%D$ */
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74 /* git commit: $Format:%H$ */
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75 /* commit time: $Format:%ai$ */