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[proxmark3-svn] / common / random.c
1 #include "random.h"
2
3 static uint32_t g_nextrandom;
4
5 /* Generates a (non-cryptographically secure) 32-bit random number.
6 *
7 * We don't have an implementation of the "rand" function. Instead we use a
8 * method of seeding with the time it took to call "autoseed" from first run.
9 *
10 * https://github.com/Proxmark/proxmark3/pull/209/commits/f9c1dcd9f6e68a8c07cffed697a9c4c8caed6015
11 *
12 * Iceman, rand needs to be fast.
13 * https://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/
14 */
15
16 inline void fast_prand(){
17 fast_prandEx(GetTickCount());
18 }
19 inline void fast_prandEx(uint32_t seed) {
20 g_nextrandom = seed;
21 }
22
23 uint32_t prand() {
24 // g_nextrandom *= 6364136223846793005;
25 // g_nextrandom += 1;
26 //return (uint32_t)(g_nextrandom >> 32) % 0xffffffff;
27 g_nextrandom = (214013 * g_nextrandom + 2531011);
28 return (g_nextrandom>>16) & 0xFFFF;
29 }
30
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