Greg Steiert / pegasus_dev

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Dependents:   blinky_max32630fthr

features/FEATURE_COMMON_PAL/mbed-client-randlib/source/randLIB.c@0:5c4d7b2438d3, 2016-11-11 (annotated)

Committer:
switches
Date:
Fri Nov 11 20:59:50 2016 +0000
Revision:
0:5c4d7b2438d3
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
switches 0:5c4d7b2438d3 1 /*
switches 0:5c4d7b2438d3 2 * Copyright (c) 2014-2015 ARM Limited. All rights reserved.
switches 0:5c4d7b2438d3 3 * SPDX-License-Identifier: Apache-2.0
switches 0:5c4d7b2438d3 4 * Licensed under the Apache License, Version 2.0 (the License); you may
switches 0:5c4d7b2438d3 5 * not use this file except in compliance with the License.
switches 0:5c4d7b2438d3 6 * You may obtain a copy of the License at
switches 0:5c4d7b2438d3 7 *
switches 0:5c4d7b2438d3 8 * http://www.apache.org/licenses/LICENSE-2.0
switches 0:5c4d7b2438d3 9 *
switches 0:5c4d7b2438d3 10 * Unless required by applicable law or agreed to in writing, software
switches 0:5c4d7b2438d3 11 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
switches 0:5c4d7b2438d3 12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
switches 0:5c4d7b2438d3 13 * See the License for the specific language governing permissions and
switches 0:5c4d7b2438d3 14 * limitations under the License.
switches 0:5c4d7b2438d3 15 */
switches 0:5c4d7b2438d3 16 #include <stdint.h>
switches 0:5c4d7b2438d3 17 #include <stdlib.h>
switches 0:5c4d7b2438d3 18 #include <stdbool.h>
switches 0:5c4d7b2438d3 19 #include <limits.h>
switches 0:5c4d7b2438d3 20 #include "randLIB.h"
switches 0:5c4d7b2438d3 21 #include "platform/arm_hal_random.h"
switches 0:5c4d7b2438d3 22
switches 0:5c4d7b2438d3 23 #if ((RAND_MAX+1) & RAND_MAX) != 0
switches 0:5c4d7b2438d3 24 #error "RAND_MAX isn't 2^n-1 :("
switches 0:5c4d7b2438d3 25 #endif
switches 0:5c4d7b2438d3 26
switches 0:5c4d7b2438d3 27 /**
switches 0:5c4d7b2438d3 28 * This library is made for getting random numbers for Timing needs in protocols.
switches 0:5c4d7b2438d3 29 *
switches 0:5c4d7b2438d3 30 * **not safe to use for security or cryptographic operations.**
switches 0:5c4d7b2438d3 31 *
switches 0:5c4d7b2438d3 32 */
switches 0:5c4d7b2438d3 33
switches 0:5c4d7b2438d3 34
switches 0:5c4d7b2438d3 35 /**
switches 0:5c4d7b2438d3 36 * \brief Init seed for Pseudo Random.
switches 0:5c4d7b2438d3 37 *
switches 0:5c4d7b2438d3 38 * \return None
switches 0:5c4d7b2438d3 39 *
switches 0:5c4d7b2438d3 40 */
switches 0:5c4d7b2438d3 41 void randLIB_seed_random(void)
switches 0:5c4d7b2438d3 42 {
switches 0:5c4d7b2438d3 43 uint32_t rand_seed;
switches 0:5c4d7b2438d3 44 arm_random_module_init();
switches 0:5c4d7b2438d3 45 rand_seed = arm_random_seed_get();
switches 0:5c4d7b2438d3 46 srand(rand_seed);
switches 0:5c4d7b2438d3 47 }
switches 0:5c4d7b2438d3 48
switches 0:5c4d7b2438d3 49 /**
switches 0:5c4d7b2438d3 50 * \brief Generate 8-bit random number.
switches 0:5c4d7b2438d3 51 *
switches 0:5c4d7b2438d3 52 * \param None
switches 0:5c4d7b2438d3 53 * \return 8-bit random number
switches 0:5c4d7b2438d3 54 *
switches 0:5c4d7b2438d3 55 */
switches 0:5c4d7b2438d3 56 uint8_t randLIB_get_8bit(void)
switches 0:5c4d7b2438d3 57 {
switches 0:5c4d7b2438d3 58 return rand();
switches 0:5c4d7b2438d3 59 }
switches 0:5c4d7b2438d3 60
switches 0:5c4d7b2438d3 61 /**
switches 0:5c4d7b2438d3 62 * \brief Generate 16-bit random number.
switches 0:5c4d7b2438d3 63 *
switches 0:5c4d7b2438d3 64 * \param None
switches 0:5c4d7b2438d3 65 * \return 16-bit random number
switches 0:5c4d7b2438d3 66 *
switches 0:5c4d7b2438d3 67 */
switches 0:5c4d7b2438d3 68 uint16_t randLIB_get_16bit(void)
switches 0:5c4d7b2438d3 69 {
switches 0:5c4d7b2438d3 70 uint16_t ret_val;
switches 0:5c4d7b2438d3 71
switches 0:5c4d7b2438d3 72 ret_val = rand();
switches 0:5c4d7b2438d3 73 #if RAND_MAX == 0x7FFF
switches 0:5c4d7b2438d3 74 ret_val |= (uint16_t) rand() << 15;
switches 0:5c4d7b2438d3 75 #endif
switches 0:5c4d7b2438d3 76
switches 0:5c4d7b2438d3 77 return ret_val;
switches 0:5c4d7b2438d3 78 }
switches 0:5c4d7b2438d3 79 /**
switches 0:5c4d7b2438d3 80 * \brief Generate 32-bit random number.
switches 0:5c4d7b2438d3 81 *
switches 0:5c4d7b2438d3 82 * \param None
switches 0:5c4d7b2438d3 83 * \return 32-bit random number
switches 0:5c4d7b2438d3 84 *
switches 0:5c4d7b2438d3 85 */
switches 0:5c4d7b2438d3 86 uint32_t randLIB_get_32bit(void)
switches 0:5c4d7b2438d3 87 {
switches 0:5c4d7b2438d3 88 uint32_t ret_val;
switches 0:5c4d7b2438d3 89
switches 0:5c4d7b2438d3 90 ret_val = rand();
switches 0:5c4d7b2438d3 91 #if RAND_MAX == 0x7FFF
switches 0:5c4d7b2438d3 92 ret_val |= (uint32_t) rand() << 15;
switches 0:5c4d7b2438d3 93 ret_val |= (uint32_t) rand() << 30;
switches 0:5c4d7b2438d3 94 #elif RAND_MAX == 0x3FFFFFFF /* IAR */
switches 0:5c4d7b2438d3 95 ret_val |= (uint32_t) rand() << 30;
switches 0:5c4d7b2438d3 96 #elif RAND_MAX == 0x7FFFFFFF
switches 0:5c4d7b2438d3 97 ret_val |= (uint32_t) rand() << 31;
switches 0:5c4d7b2438d3 98 #else
switches 0:5c4d7b2438d3 99 #error "randLIB_get_32bit - odd RAND_MAX"
switches 0:5c4d7b2438d3 100 #endif
switches 0:5c4d7b2438d3 101
switches 0:5c4d7b2438d3 102 return ret_val;
switches 0:5c4d7b2438d3 103 }
switches 0:5c4d7b2438d3 104
switches 0:5c4d7b2438d3 105
switches 0:5c4d7b2438d3 106 /**
switches 0:5c4d7b2438d3 107 * \brief Generate n-bytes random numbers.
switches 0:5c4d7b2438d3 108 *
switches 0:5c4d7b2438d3 109 * \param data_ptr pointer where random will be stored
switches 0:5c4d7b2438d3 110 * \param eight_bit_boundary how many bytes need random
switches 0:5c4d7b2438d3 111 * \return 0 process valid
switches 0:5c4d7b2438d3 112 * \return -1 Unsupported Parameters
switches 0:5c4d7b2438d3 113 *
switches 0:5c4d7b2438d3 114 */
switches 0:5c4d7b2438d3 115 int8_t randLIB_get_n_bytes_random(uint8_t *data_ptr, uint8_t eight_bit_boundary)
switches 0:5c4d7b2438d3 116 {
switches 0:5c4d7b2438d3 117 if ((data_ptr == 0) || (eight_bit_boundary == 0)) {
switches 0:5c4d7b2438d3 118 return -1;
switches 0:5c4d7b2438d3 119 }
switches 0:5c4d7b2438d3 120
switches 0:5c4d7b2438d3 121 while (eight_bit_boundary) {
switches 0:5c4d7b2438d3 122 *data_ptr++ = randLIB_get_8bit();
switches 0:5c4d7b2438d3 123 eight_bit_boundary--;
switches 0:5c4d7b2438d3 124 }
switches 0:5c4d7b2438d3 125 return 0;
switches 0:5c4d7b2438d3 126 }
switches 0:5c4d7b2438d3 127
switches 0:5c4d7b2438d3 128 /**
switches 0:5c4d7b2438d3 129 * \brief Generate a random number within a range.
switches 0:5c4d7b2438d3 130 *
switches 0:5c4d7b2438d3 131 * The result is linearly distributed in the range [min..max], inclusive.
switches 0:5c4d7b2438d3 132 *
switches 0:5c4d7b2438d3 133 * \param min minimum value that can be generated
switches 0:5c4d7b2438d3 134 * \param max maximum value that can be generated
switches 0:5c4d7b2438d3 135 */
switches 0:5c4d7b2438d3 136 uint16_t randLIB_get_random_in_range(uint16_t min, uint16_t max)
switches 0:5c4d7b2438d3 137 {
switches 0:5c4d7b2438d3 138 /* This special case is potentially common, particularly in this routine's
switches 0:5c4d7b2438d3 139 * first user (Trickle), so worth catching immediately */
switches 0:5c4d7b2438d3 140 if (min == max) {
switches 0:5c4d7b2438d3 141 return min;
switches 0:5c4d7b2438d3 142 }
switches 0:5c4d7b2438d3 143
switches 0:5c4d7b2438d3 144 /* 16-bit arithmetic below fails in this extreme case; we can optimise it */
switches 0:5c4d7b2438d3 145 if (max - min == 0xFFFF) {
switches 0:5c4d7b2438d3 146 return randLIB_get_16bit();
switches 0:5c4d7b2438d3 147 }
switches 0:5c4d7b2438d3 148
switches 0:5c4d7b2438d3 149 /* We get RAND_MAX+1 values from rand() in the range [0..RAND_MAX], and
switches 0:5c4d7b2438d3 150 * need to divvy them up into the number of values we need. And reroll any
switches 0:5c4d7b2438d3 151 * odd values off the end as we insist every value having equal chance.
switches 0:5c4d7b2438d3 152 *
switches 0:5c4d7b2438d3 153 * Special handling for systems where RAND_MAX is 0x7FFF; we use our
switches 0:5c4d7b2438d3 154 * randLIB_get_16bit() and have to be a bit more careful about
switches 0:5c4d7b2438d3 155 * unsigned integer overflow. (On other systems rand() returns int,
switches 0:5c4d7b2438d3 156 * so we can't overflow if we use unsigned int).
switches 0:5c4d7b2438d3 157 *
switches 0:5c4d7b2438d3 158 * Eg, range(1,3), RAND_MAX = 0x7FFFFFFF:
switches 0:5c4d7b2438d3 159 * We have 3 bands of size 0x2AAAAAAA (0x80000000/3).
switches 0:5c4d7b2438d3 160 *
switches 0:5c4d7b2438d3 161 * We roll: 0x00000000..0x2AAAAAAA9 -> 1
switches 0:5c4d7b2438d3 162 * 0x2AAAAAAA..0x555555553 -> 2
switches 0:5c4d7b2438d3 163 * 0x55555554..0x7FFFFFFFD -> 3
switches 0:5c4d7b2438d3 164 * 0x7FFFFFFE..0x7FFFFFFFF -> reroll
switches 0:5c4d7b2438d3 165 *
switches 0:5c4d7b2438d3 166 * (Bias problem clearly pretty insignificant there, but gets worse as
switches 0:5c4d7b2438d3 167 * range increases).
switches 0:5c4d7b2438d3 168 */
switches 0:5c4d7b2438d3 169 unsigned int values_needed = max + 1 - min;
switches 0:5c4d7b2438d3 170 #if RAND_MAX > 0xFFFF
switches 0:5c4d7b2438d3 171 unsigned int band_size = (RAND_MAX + 1u) / values_needed;
switches 0:5c4d7b2438d3 172 #elif UINT_MAX > 0xFFFF
switches 0:5c4d7b2438d3 173 unsigned int band_size = 0x10000u / values_needed;
switches 0:5c4d7b2438d3 174 #else
switches 0:5c4d7b2438d3 175 /* Avoid the need for long division, at the expense of fractionally
switches 0:5c4d7b2438d3 176 * increasing reroll chance. */
switches 0:5c4d7b2438d3 177 unsigned int band_size = 0xFFFFu / values_needed;
switches 0:5c4d7b2438d3 178 #endif
switches 0:5c4d7b2438d3 179 unsigned int top_of_bands = band_size * values_needed;
switches 0:5c4d7b2438d3 180 unsigned int result;
switches 0:5c4d7b2438d3 181 do {
switches 0:5c4d7b2438d3 182 #if RAND_MAX > 0xFFFF
switches 0:5c4d7b2438d3 183 result = rand();
switches 0:5c4d7b2438d3 184 #else
switches 0:5c4d7b2438d3 185 result = randLIB_get_16bit();
switches 0:5c4d7b2438d3 186 #endif
switches 0:5c4d7b2438d3 187 } while (result >= top_of_bands);
switches 0:5c4d7b2438d3 188
switches 0:5c4d7b2438d3 189 return min + (uint16_t)(result / band_size);
switches 0:5c4d7b2438d3 190 }
switches 0:5c4d7b2438d3 191
switches 0:5c4d7b2438d3 192 /**
switches 0:5c4d7b2438d3 193 * \brief Randomise a base 32-bit number by a jitter factor
switches 0:5c4d7b2438d3 194 *
switches 0:5c4d7b2438d3 195 * The result is linearly distributed in the jitter range, which is expressed
switches 0:5c4d7b2438d3 196 * as fixed-point unsigned 1.15 values. For example, to produce a number in the
switches 0:5c4d7b2438d3 197 * range [0.75 * base, 1.25 * base], set min_factor to 0x6000 and max_factor to
switches 0:5c4d7b2438d3 198 * 0xA000.
switches 0:5c4d7b2438d3 199 *
switches 0:5c4d7b2438d3 200 * Result is clamped to 0xFFFFFFFF if it overflows.
switches 0:5c4d7b2438d3 201 *
switches 0:5c4d7b2438d3 202 * \param base The base 32-bit value
switches 0:5c4d7b2438d3 203 * \param min_factor The minimum value for the random factor
switches 0:5c4d7b2438d3 204 * \param max_factor The maximum value for the random factor
switches 0:5c4d7b2438d3 205 */
switches 0:5c4d7b2438d3 206 uint32_t randLIB_randomise_base(uint32_t base, uint16_t min_factor, uint16_t max_factor)
switches 0:5c4d7b2438d3 207 {
switches 0:5c4d7b2438d3 208 uint16_t random_factor = randLIB_get_random_in_range(min_factor, max_factor);
switches 0:5c4d7b2438d3 209
switches 0:5c4d7b2438d3 210 /* 32x16-bit long multiplication, to get 48-bit result */
switches 0:5c4d7b2438d3 211 uint32_t hi = (base >> 16) * random_factor;
switches 0:5c4d7b2438d3 212 uint32_t lo = (base & 0xFFFF) * random_factor;
switches 0:5c4d7b2438d3 213 /* Add halves, and take top 32 bits of 48-bit result */
switches 0:5c4d7b2438d3 214 uint32_t res = hi + (lo >> 16);
switches 0:5c4d7b2438d3 215
switches 0:5c4d7b2438d3 216 /* Randomisation factor is *2^15, so need to shift up 1 more bit, avoiding overflow */
switches 0:5c4d7b2438d3 217 if (res & 0x80000000) {
switches 0:5c4d7b2438d3 218 res = 0xFFFFFFFF;
switches 0:5c4d7b2438d3 219 } else {
switches 0:5c4d7b2438d3 220 res = (res << 1) | ((lo >> 15) & 1);
switches 0:5c4d7b2438d3 221 }
switches 0:5c4d7b2438d3 222
switches 0:5c4d7b2438d3 223 return res;
switches 0:5c4d7b2438d3 224 }