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454 lines
10 KiB
C
454 lines
10 KiB
C
/*
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* neug.c - random number generation (from NeuG/src/random.c)
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*
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* Copyright (C) 2011 Free Software Initiative of Japan
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* Author: NIIBE Yutaka <gniibe@fsij.org>
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*
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* This file is a part of NeuG, a Random Number Generator
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* implementation (for STM32F103).
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*
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* NeuG is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Gnuk is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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* License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "config.h"
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#include "ch.h"
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#include "hal.h"
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static Thread *rng_thread;
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#define ADC_DATA_AVAILABLE ((eventmask_t)1)
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/* Total number of channels to be sampled by a single ADC operation.*/
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#define ADC_GRP1_NUM_CHANNELS 2
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/* Depth of the conversion buffer, channels are sampled one time each.*/
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#define ADC_GRP1_BUF_DEPTH 4
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/*
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* ADC samples buffer.
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*/
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static adcsample_t samp[ADC_GRP1_NUM_CHANNELS * ADC_GRP1_BUF_DEPTH];
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static void adccb (adcsample_t *buffer, size_t n);
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/*
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* ADC conversion group.
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* Mode: Linear buffer, 4 samples of 2 channels, SW triggered.
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* Channels: Vref (1.5 cycles sample time, violating the spec.)
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* Sensor (1.5 cycles sample time, violating the spec.)
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*/
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static const ADCConversionGroup adcgrpcfg = {
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FALSE,
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ADC_GRP1_NUM_CHANNELS,
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0,
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ADC_CR2_EXTSEL_SWSTART | ADC_CR2_TSVREFE | ADC_CR2_CONT,
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ADC_SMPR1_SMP_SENSOR(ADC_SAMPLE_1P5) | ADC_SMPR1_SMP_VREF(ADC_SAMPLE_1P5),
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0,
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ADC_SQR1_NUM_CH(ADC_GRP1_NUM_CHANNELS),
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0,
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ADC_SQR3_SQ2_N(ADC_CHANNEL_SENSOR) | ADC_SQR3_SQ1_N(ADC_CHANNEL_VREFINT)
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};
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/*
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* ADC end conversion callback.
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*/
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static void adccb (adcsample_t *buffer, size_t n)
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{
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ADCDriver *adcp = &ADCD1;
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(void) buffer; (void) n;
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if (adcp->ad_state == ADC_COMPLETE)
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chEvtSignalI (rng_thread, ADC_DATA_AVAILABLE);
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}
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/*
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* TinyMT routines.
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*
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* See
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* "Tiny Mersenne Twister (TinyMT): A small-sized variant of Mersenne Twister"
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* by Mutsuo Saito and Makoto Matsumoto
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* http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/TINYMT/
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*/
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/* Use the first example of TinyMT */
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#define TMT_MAT1 0x8f7011ee
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#define TMT_MAT2 0xfc78ff1f
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#define TMT_TMAT 0x3793fdff
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static uint32_t tmt[4];
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static void tmt_one_step (void);
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#define TMT_INIT_MIN_LOOP 8
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#define TMT_INIT_PRE_LOOP 8
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/**
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* @brief TinyMT initialize function.
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*/
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static void tmt_init (uint32_t seed)
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{
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int i;
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tmt[0] = seed;
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tmt[1] = TMT_MAT1;
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tmt[2] = TMT_MAT2;
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tmt[3] = TMT_TMAT;
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for (i = 1; i < TMT_INIT_MIN_LOOP; i++)
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tmt[i & 3] ^= i + UINT32_C(1812433253) * (tmt[(i - 1) & 3]
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^ (tmt[(i - 1) & 3] >> 30));
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if ((tmt[0] & 0x7fffffff) == 0 && tmt[1] == 0 && tmt[2] == 0 && tmt[3] == 0)
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{ /* Prevent all zero */
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tmt[0] = 'T';
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tmt[1] = 'I';
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tmt[2] = 'N';
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tmt[3] = 'Y';
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}
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for (i = 0; i < TMT_INIT_PRE_LOOP; i++)
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tmt_one_step ();
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}
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/**
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* @brief TinyMT one step function, call this every time before tmt_value.
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*/
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static void tmt_one_step (void)
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{
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uint32_t x, y;
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y = tmt[3];
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x = (tmt[0] & 0x7fffffff) ^ tmt[1] ^ tmt[2];
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x ^= (x << 1);
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y ^= (y >> 1) ^ x;
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tmt[0] = tmt[1];
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tmt[1] = tmt[2];
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tmt[2] = x ^ (y << 10);
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tmt[3] = y;
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if ((y & 1))
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{
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tmt[1] ^= TMT_MAT1;
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tmt[2] ^= TMT_MAT2;
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}
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}
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/**
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* @brief Get a random word (32-bit).
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*/
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static uint32_t tmt_value (void)
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{
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uint32_t t0, t1;
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t0 = tmt[3];
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t1 = tmt[0] + (tmt[2] >> 8);
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t0 ^= t1;
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if ((t1 & 1))
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t0 ^= TMT_TMAT;
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return t0;
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}
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/* 8 parallel CRC-16 shift registers, with randomly rotated feedback */
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#define EPOOL_SIZE 16
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static uint8_t epool[EPOOL_SIZE]; /* Big-endian */
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static uint8_t ep_count;
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/*
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* Magic number seven.
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*
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* We did an experiment of measuring entropy of ADC output with MUST.
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* The entropy of a byte by raw sampling of LSBs has more than 6.0 bit/byte.
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* So, it is considered OK to get 4-byte from 7-byte (6x7 = 42 > 32).
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*/
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#define NUM_NOISE_INPUTS 7
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#define SHIFT_RIGHT(f) ((f)>>1)
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static void ep_add (uint8_t entropy_bits, uint8_t another_random_bit)
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{
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uint8_t v = epool[ep_count];
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/* CRC-16-CCITT's Polynomial is: x^16 + x^12 + x^5 + 1 */
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epool[(ep_count - 12)& 0x0f] ^= v;
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epool[(ep_count - 5)& 0x0f] ^= v;
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epool[ep_count] = SHIFT_RIGHT (v) ^ entropy_bits;
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if ((v&1) || another_random_bit)
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epool[ep_count] ^= 0xff;
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ep_count = (ep_count + 1) & 0x0f;
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}
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#define FNV_INIT 2166136261U
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#define FNV_PRIME 16777619
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static uint32_t fnv32_hash (const uint8_t *buf, int len)
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{
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uint32_t v = FNV_INIT;
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int i;
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for (i = 0; i < len; i++)
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{
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v ^= buf[i];
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v *= FNV_PRIME;
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}
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return v;
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}
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#define PROBABILITY_50_BY_TICK() ((SysTick->VAL & 0x02) != 0)
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static uint32_t ep_output (void)
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{
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int i;
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uint8_t buf[NUM_NOISE_INPUTS];
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uint8_t *p = buf;
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/*
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* NUM_NOISE_INPUTS is seven.
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*
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* There are sixteen bytes in the CRC-16 buffer. We use seven
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* outputs of CRC-16 buffer for final output. There are two parts;
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* former 4 outputs which will be used directly, and latter 3
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* outputs which will be used with feedback loop.
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*/
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/* At some probability, use latter 3 outputs of CRC-16 buffer */
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for (i = NUM_NOISE_INPUTS - 1; i >= 4; i--)
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if (PROBABILITY_50_BY_TICK ())
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*p++ = epool[(ep_count+i) & 0x0f] ^ epool[(ep_count+i-4) & 0x0f];
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/* Use former 4 outputs of CRC-16 buffer */
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for (i = 3; i >= 0; i--)
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*p++ = epool[(ep_count+i) & 0x0f];
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return fnv32_hash (buf, p - buf);
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}
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/*
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* Ring buffer, filled by generator, consumed by neug_get routine.
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*/
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struct rng_rb {
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uint32_t *buf;
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Mutex m;
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CondVar data_available;
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CondVar space_available;
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uint8_t head, tail;
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uint8_t size;
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unsigned int full :1;
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unsigned int empty :1;
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};
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static void rb_init (struct rng_rb *rb, uint32_t *p, uint8_t size)
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{
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rb->buf = p;
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rb->size = size;
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chMtxInit (&rb->m);
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chCondInit (&rb->data_available);
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chCondInit (&rb->space_available);
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rb->head = rb->tail = 0;
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rb->full = 0;
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rb->empty = 1;
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}
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static void rb_add (struct rng_rb *rb, uint32_t v)
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{
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rb->buf[rb->tail++] = v;
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if (rb->tail == rb->size)
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rb->tail = 0;
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if (rb->tail == rb->head)
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rb->full = 1;
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rb->empty = 0;
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}
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static uint32_t rb_del (struct rng_rb *rb)
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{
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uint32_t v = rb->buf[rb->head++];
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if (rb->head == rb->size)
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rb->head = 0;
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if (rb->head == rb->tail)
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rb->empty = 1;
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rb->full = 0;
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return v;
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}
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/**
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* @brief Random number generation from ADC sampling.
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* @param RB: Pointer to ring buffer structure
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* @return -1 when failure, 0 otherwise.
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* @note Called holding the mutex, with RB->full == 0.
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* Keep generating until RB->full == 1.
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*/
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static int rng_gen (struct rng_rb *rb)
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{
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static uint8_t round = 0;
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uint8_t b;
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while (1)
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{
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chEvtWaitOne (ADC_DATA_AVAILABLE);
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/* Got, ADC sampling data */
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round++;
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b = (((samp[0] & 0x01) << 0) | ((samp[1] & 0x01) << 1)
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| ((samp[2] & 0x01) << 2) | ((samp[3] & 0x01) << 3)
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| ((samp[4] & 0x01) << 4) | ((samp[5] & 0x01) << 5)
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| ((samp[6] & 0x01) << 6) | ((samp[7] & 0x01) << 7));
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adcStartConversion (&ADCD1, &adcgrpcfg, samp, ADC_GRP1_BUF_DEPTH, adccb);
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/*
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* Put a random byte to entropy pool.
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*/
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ep_add (b, PROBABILITY_50_BY_TICK ());
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if ((round % NUM_NOISE_INPUTS) == 0)
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{ /* We have enough entropy in the pool. */
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uint32_t v = ep_output (); /* Get the random bits from the pool. */
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/* Mix the random bits from the pool with the output of PRNG. */
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tmt_one_step ();
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v ^= tmt_value ();
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/* We got the final random bits, add it to the ring buffer. */
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rb_add (rb, v);
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round = 0;
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if (rb->full)
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/* fully generated */
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break;
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}
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}
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return 0; /* success */
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}
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/**
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* @brief Random number generation thread.
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*/
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static msg_t rng (void *arg)
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{
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struct rng_rb *rb = (struct rng_rb *)arg;
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rng_thread = chThdSelf ();
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adcStart (&ADCD1, NULL);
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adcStartConversion (&ADCD1, &adcgrpcfg, samp, ADC_GRP1_BUF_DEPTH, adccb);
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while (1)
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{
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chMtxLock (&rb->m);
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while (rb->full)
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chCondWait (&rb->space_available);
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rng_gen (rb);
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chCondSignal (&rb->data_available);
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chMtxUnlock ();
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}
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return 0;
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}
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static struct rng_rb the_ring_buffer;
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static WORKING_AREA(wa_rng, 128);
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/**
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* @brief Initialize NeuG.
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*/
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void
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neug_init (uint32_t *buf, uint8_t size)
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{
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struct rng_rb *rb = &the_ring_buffer;
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tmt_init (0);
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rb_init (rb, buf, size);
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chThdCreateStatic (wa_rng, sizeof (wa_rng), NORMALPRIO, rng, rb);
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}
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/**
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* @breif Flush random bytes.
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*/
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void
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neug_flush (void)
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{
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struct rng_rb *rb = &the_ring_buffer;
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chMtxLock (&rb->m);
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while (!rb->empty)
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(void)rb_del (rb);
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chCondSignal (&rb->space_available);
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chMtxUnlock ();
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}
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/**
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* @breif Set seed to PRNG
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*/
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void
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neug_prng_reseed (void)
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{
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uint32_t seed = ep_output ();
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tmt_init (seed);
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neug_flush ();
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}
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/**
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* @brief Wakes up RNG thread to generate random numbers.
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*/
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void
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neug_kick_filling (void)
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{
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struct rng_rb *rb = &the_ring_buffer;
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chMtxLock (&rb->m);
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if (!rb->full)
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chCondSignal (&rb->space_available);
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chMtxUnlock ();
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}
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/**
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* @brief Get random word (32-bit) from NeuG.
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* @detail With NEUG_KICK_FILLING, it wakes up RNG thread.
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* With NEUG_NO_KICK, it doesn't wake up RNG thread automatically,
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* it is needed to call neug_kick_filling later.
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*/
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uint32_t
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neug_get (int kick)
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{
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struct rng_rb *rb = &the_ring_buffer;
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uint32_t v;
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chMtxLock (&rb->m);
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while (rb->empty)
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chCondWait (&rb->data_available);
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v = rb_del (rb);
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if (kick)
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chCondSignal (&rb->space_available);
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chMtxUnlock ();
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return v;
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}
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void
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neug_wait_full (void)
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{
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struct rng_rb *rb = &the_ring_buffer;
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chMtxLock (&rb->m);
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while (!rb->full)
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chCondWait (&rb->data_available);
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chMtxUnlock ();
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}
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