- initial import
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367
src/libs/srtp/crypto/math/stat.c
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367
src/libs/srtp/crypto/math/stat.c
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/*
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* stats.c
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*
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* statistical tests for randomness (FIPS 140-2, Section 4.9)
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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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#include "stat.h"
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debug_module_t 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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err_status_t
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stat_test_monobit(uint8_t *data) {
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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(mod_stat, "bit count: %d", ones_count);
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if ((ones_count < 9725) || (ones_count > 10275))
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return err_status_algo_fail;
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return err_status_ok;
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}
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err_status_t
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stat_test_poker(uint8_t *data) {
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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] = {
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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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(mod_stat, "poker test: %f\n", poker);
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if ((poker < 2.16) || (poker > 46.17))
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return err_status_algo_fail;
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return 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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err_status_t
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stat_test_runs(uint8_t *data) {
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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(mod_stat, ">25 runs: %d", state);
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return 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(mod_stat, ">25 gaps: %d", state);
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return err_status_algo_fail; /* long-runs test 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(mod_stat, ">25 runs (2): %d", state);
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return err_status_algo_fail; /* long-runs test 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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state--;
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/* check for long gaps */
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if (state < -25) {
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debug_print(mod_stat, ">25 gaps (2): %d", state);
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return 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 (mod_stat.on) {
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debug_print(mod_stat, "runs test", NULL);
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for (i=0; i < 6; i++)
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debug_print(mod_stat, " runs[]: %d", runs[i]);
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for (i=0; i < 6; i++)
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debug_print(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 err_status_algo_fail;
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return err_status_ok;
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}
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/*
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* the function stat_test_rand_source applys the FIPS-140-2 statistical
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* tests to the random source defined by rs
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*
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*/
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#define RAND_SRC_BUF_OCTETS 50 /* this value MUST divide 2500! */
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err_status_t
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stat_test_rand_source(rand_source_func_t get_rand_bytes) {
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int i;
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double poker;
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uint8_t *data, *data_end;
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uint16_t f[16] = {
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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uint8_t buffer[RAND_SRC_BUF_OCTETS];
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err_status_t status;
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int ones_count = 0;
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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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/* counters for monobit, poker, and runs tests are initialized above */
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/* main loop: fill buffer, update counters for stat tests */
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for (i=0; i < 2500; i+=RAND_SRC_BUF_OCTETS) {
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/* fill data buffer */
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status = get_rand_bytes(buffer, RAND_SRC_BUF_OCTETS);
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if (status) {
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debug_print(mod_stat, "couldn't get rand bytes: %d",status);
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return status;
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}
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#if 0
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debug_print(mod_stat, "%s",
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octet_string_hex_string(buffer, RAND_SRC_BUF_OCTETS));
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#endif
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data = buffer;
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data_end = data + RAND_SRC_BUF_OCTETS;
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while (data < data_end) {
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/* update monobit test counter */
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ones_count += octet_get_weight(*data);
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/* update poker test counters */
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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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/* update runs test counters */
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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(mod_stat, ">25 runs (3): %d", state);
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return 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(mod_stat, ">25 gaps (3): %d", state);
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return err_status_algo_fail; /* long-runs test 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(mod_stat, ">25 runs (4): %d", state);
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return err_status_algo_fail; /* long-runs test 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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state--;
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/* check for long gaps */
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if (state < -25) {
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debug_print(mod_stat, ">25 gaps (4): %d", state);
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return 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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/* advance data pointer */
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data++;
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}
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}
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/* check to see if test data is within bounds */
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/* check monobit test data */
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debug_print(mod_stat, "stat: bit count: %d", ones_count);
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if ((ones_count < 9725) || (ones_count > 10275)) {
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debug_print(mod_stat, "stat: failed monobit test %d", ones_count);
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return err_status_algo_fail;
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}
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/* check poker test data */
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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(mod_stat, "stat: poker test: %f", poker);
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if ((poker < 2.16) || (poker > 46.17)) {
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debug_print(mod_stat, "stat: failed poker test", NULL);
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return err_status_algo_fail;
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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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debug_print(mod_stat, "stat: failed run/gap test", NULL);
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return err_status_algo_fail;
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}
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debug_print(mod_stat, "passed random stat test", NULL);
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return err_status_ok;
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}
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err_status_t
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stat_test_rand_source_with_repetition(rand_source_func_t source, unsigned num_trials) {
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unsigned int i;
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err_status_t err = err_status_algo_fail;
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for (i=0; i < num_trials; i++) {
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err = stat_test_rand_source(source);
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if (err == err_status_ok) {
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return err_status_ok;
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}
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debug_print(mod_stat, "failed stat test (try number %d)\n", i);
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}
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return err;
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}
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