kopia lustrzana https://github.com/solokeys/solo1
93 wiersze
1.8 KiB
C
93 wiersze
1.8 KiB
C
// Copyright 2019 SoloKeys Developers
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//
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// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
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// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
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// http://opensource.org/licenses/MIT>, at your option. This file may not be
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// copied, modified, or distributed except according to those terms.
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#include <math.h>
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "stm32l4xx_ll_rng.h"
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#include "rng.h"
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#include "log.h"
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int __errno = 0;
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void rng_get_bytes(uint8_t * dst, size_t sz)
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{
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uint8_t r[8];
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unsigned int i,j;
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for (i = 0; i < sz; i += 4)
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{
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while( !LL_RNG_IsActiveFlag_DRDY(RNG) )
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;
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*(uint32_t*)&r = LL_RNG_ReadRandData32(RNG);
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if (RNG->SR & 0x66)
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{
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printf2(TAG_ERR,"Error RNG: %02lx\r\n", RNG->SR);
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exit(1);
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}
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for (j = 0; j < 4; j++)
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{
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if ((i + j) > sz)
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{
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return;
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}
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dst[i + j] = r[j];
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}
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}
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}
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float shannon_entropy(float * p, size_t sz)
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{
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unsigned int i;
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float entropy = 0.0f;
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for(i=0; i < sz; i++)
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{
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if (p[i] > 0.0)
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{
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entropy -= p[i] * (float) log( (double) p[i]);
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}
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}
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entropy = entropy / (float) log ((double) 2.0);
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return entropy;
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}
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// Measure shannon entropy of RNG
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float rng_test(size_t n)
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{
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unsigned int i;
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int sz = 0;
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uint8_t buf[4];
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int counts[256];
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float p[256];
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memset(counts, 0, sizeof(counts));
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for(i=0; i < n; i+=4)
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{
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rng_get_bytes(buf, 4);
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sz += 4;
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counts[buf[0]]++;
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counts[buf[1]]++;
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counts[buf[2]]++;
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counts[buf[3]]++;
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}
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for (i = 0; i < 256; i++)
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{
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p[i] = ((float)counts[i])/sz;
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}
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return shannon_entropy(p, 256);
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}
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