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Code Issues Releases Wiki Activity

import random_uniform and random_permute functions from TREZOR codebase

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This commit is contained in:
Pavol Rusnak 2015-03-30 17:45:34 +02:00
parent ad71a16e61
commit 196cabe012
2 changed files with 25 additions and 5 deletions
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26
rand.c
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@ -35,10 +35,9 @@ void init_rand(void)
int finalize_rand(void) int finalize_rand(void)
{ {
int err = fclose(f); int err = fclose(f);
f = NULL; f = NULL;
return err;
return err;
} }
uint32_t random32(void) uint32_t random32(void)
@ -50,8 +49,27 @@ uint32_t random32(void)
return r; return r;
} }
uint32_t random_uniform(uint32_t n)
{
uint32_t x, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
while ((x = random32()) >= max);
return x / (max / n);
}
void random_buffer(uint8_t *buf, size_t len) void random_buffer(uint8_t *buf, size_t len)
{ {
size_t len_read = fread(buf, 1, len, f); size_t len_read = fread(buf, 1, len, f);
assert(len_read == len); assert(len_read == len);
} }
void random_permute(char *str, size_t len)
{
int i, j;
char t;
for (i = len - 1; i >= 1; i--) {
j = random_uniform(i + 1);
t = str[j];
str[j] = str[i];
str[i] = t;
}
}

4
rand.h
View File

@ -24,12 +24,14 @@
#ifndef __RAND_H__ #ifndef __RAND_H__
#define __RAND_H__ #define __RAND_H__
#include <stdlib.h>
#include <stdint.h> #include <stdint.h>
#include <stdlib.h>
void init_rand(void); void init_rand(void);
int finalize_rand(void); int finalize_rand(void);
uint32_t random32(void); uint32_t random32(void);
uint32_t random_uniform(uint32_t n);
void random_buffer(uint8_t *buf, size_t len); void random_buffer(uint8_t *buf, size_t len);
void random_permute(char *buf, size_t len);
#endif #endif