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211 lines
6.8 KiB
C
211 lines
6.8 KiB
C
/*
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* stats.c
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*
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* statistical tests
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*
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* David A. McGrew
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* Cisco Systems, Inc.
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*/
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/*
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*
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* Copyright (c) 2001-2017, Cisco Systems, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* Neither the name of the Cisco Systems, Inc. nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#include "config.h"
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#include "stat.h"
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srtp_debug_module_t srtp_mod_stat = {
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0, /* debugging is off by default */
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(char *)"stat test" /* printable module name */
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};
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/*
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* each test assumes that 20,000 bits (2500 octets) of data is
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* provided as input
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*/
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#define STAT_TEST_DATA_LEN 2500
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srtp_err_status_t stat_test_monobit(uint8_t *data)
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{
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uint8_t *data_end = data + STAT_TEST_DATA_LEN;
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uint16_t ones_count;
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ones_count = 0;
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while (data < data_end) {
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ones_count += octet_get_weight(*data);
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data++;
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}
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debug_print(srtp_mod_stat, "bit count: %d", ones_count);
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if ((ones_count < 9725) || (ones_count > 10275))
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return srtp_err_status_algo_fail;
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return srtp_err_status_ok;
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}
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srtp_err_status_t stat_test_poker(uint8_t *data)
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{
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int i;
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uint8_t *data_end = data + STAT_TEST_DATA_LEN;
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double poker;
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uint16_t f[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
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while (data < data_end) {
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f[*data & 0x0f]++; /* increment freq. count for low nibble */
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f[(*data) >> 4]++; /* increment freq. count for high nibble */
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data++;
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}
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poker = 0.0;
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for (i = 0; i < 16; i++)
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poker += (double)f[i] * f[i];
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poker *= (16.0 / 5000.0);
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poker -= 5000.0;
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debug_print(srtp_mod_stat, "poker test: %f\n", poker);
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if ((poker < 2.16) || (poker > 46.17))
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return srtp_err_status_algo_fail;
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return srtp_err_status_ok;
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}
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/*
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* runs[i] holds the number of runs of size (i-1)
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*/
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srtp_err_status_t stat_test_runs(uint8_t *data)
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{
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uint8_t *data_end = data + STAT_TEST_DATA_LEN;
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uint16_t runs[6] = { 0, 0, 0, 0, 0, 0 };
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uint16_t gaps[6] = { 0, 0, 0, 0, 0, 0 };
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uint16_t lo_value[6] = { 2315, 1114, 527, 240, 103, 103 };
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uint16_t hi_value[6] = { 2685, 1386, 723, 384, 209, 209 };
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int state = 0;
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uint16_t mask;
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int i;
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/*
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* the state variable holds the number of bits in the
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* current run (or gap, if negative)
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*/
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while (data < data_end) {
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/* loop over the bits of this byte */
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for (mask = 1; mask < 256; mask <<= 1) {
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if (*data & mask) {
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/* next bit is a one */
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if (state > 0) {
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/* prefix is a run, so increment the run-count */
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state++;
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/* check for long runs */
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if (state > 25) {
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debug_print(srtp_mod_stat, ">25 runs: %d", state);
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return srtp_err_status_algo_fail;
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}
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} else if (state < 0) {
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/* prefix is a gap */
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if (state < -25) {
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debug_print(srtp_mod_stat, ">25 gaps: %d", state);
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return srtp_err_status_algo_fail; /* long-runs test
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failed */
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}
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if (state < -6) {
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state = -6; /* group together gaps > 5 */
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}
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gaps[-1 - state]++; /* increment gap count */
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state = 1; /* set state at one set bit */
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} else {
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/* state is zero; this happens only at initialization */
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state = 1;
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}
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} else {
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/* next bit is a zero */
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if (state > 0) {
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/* prefix is a run */
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if (state > 25) {
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debug_print(srtp_mod_stat, ">25 runs (2): %d", state);
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return srtp_err_status_algo_fail; /* long-runs test
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failed */
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}
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if (state > 6) {
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state = 6; /* group together runs > 5 */
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}
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runs[state - 1]++; /* increment run count */
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state = -1; /* set state at one zero bit */
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} else if (state < 0) {
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/* prefix is a gap, so increment gap-count (decrement state)
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*/
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state--;
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/* check for long gaps */
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if (state < -25) {
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debug_print(srtp_mod_stat, ">25 gaps (2): %d", state);
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return srtp_err_status_algo_fail;
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}
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} else {
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/* state is zero; this happens only at initialization */
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state = -1;
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}
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}
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}
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/* move along to next octet */
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data++;
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}
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if (srtp_mod_stat.on) {
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debug_print(srtp_mod_stat, "runs test", NULL);
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for (i = 0; i < 6; i++)
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debug_print(srtp_mod_stat, " runs[]: %d", runs[i]);
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for (i = 0; i < 6; i++)
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debug_print(srtp_mod_stat, " gaps[]: %d", gaps[i]);
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}
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/* check run and gap counts against the fixed limits */
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for (i = 0; i < 6; i++)
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if ((runs[i] < lo_value[i]) || (runs[i] > hi_value[i]) ||
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(gaps[i] < lo_value[i]) || (gaps[i] > hi_value[i]))
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return srtp_err_status_algo_fail;
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return srtp_err_status_ok;
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}
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