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-rw-r--r--srtp/crypto/math/stat.c367
1 files changed, 367 insertions, 0 deletions
diff --git a/srtp/crypto/math/stat.c b/srtp/crypto/math/stat.c
new file mode 100644
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+++ b/srtp/crypto/math/stat.c
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+/*
+ * stats.c
+ *
+ * statistical tests for randomness (FIPS 140-2, Section 4.9)
+ *
+ * David A. McGrew
+ * Cisco Systems, Inc.
+ */
+
+#include "stat.h"
+
+debug_module_t mod_stat = {
+ 0, /* debugging is off by default */
+ (char *)"stat test" /* printable module name */
+};
+
+/*
+ * each test assumes that 20,000 bits (2500 octets) of data is
+ * provided as input
+ */
+
+#define STAT_TEST_DATA_LEN 2500
+
+err_status_t
+stat_test_monobit(uint8_t *data) {
+ uint8_t *data_end = data + STAT_TEST_DATA_LEN;
+ uint16_t ones_count;
+
+ ones_count = 0;
+ while (data < data_end) {
+ ones_count += octet_get_weight(*data);
+ data++;
+ }
+
+ debug_print(mod_stat, "bit count: %d", ones_count);
+
+ if ((ones_count < 9725) || (ones_count > 10275))
+ return err_status_algo_fail;
+
+ return err_status_ok;
+}
+
+err_status_t
+stat_test_poker(uint8_t *data) {
+ int i;
+ uint8_t *data_end = data + STAT_TEST_DATA_LEN;
+ double poker;
+ uint16_t f[16] = {
+ 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0
+ };
+
+ while (data < data_end) {
+ f[*data & 0x0f]++; /* increment freq. count for low nibble */
+ f[(*data) >> 4]++; /* increment freq. count for high nibble */
+ data++;
+ }
+
+ poker = 0.0;
+ for (i=0; i < 16; i++)
+ poker += (double) f[i] * f[i];
+
+ poker *= (16.0 / 5000.0);
+ poker -= 5000.0;
+
+ debug_print(mod_stat, "poker test: %f\n", poker);
+
+ if ((poker < 2.16) || (poker > 46.17))
+ return err_status_algo_fail;
+
+ return err_status_ok;
+}
+
+
+/*
+ * runs[i] holds the number of runs of size (i-1)
+ */
+
+err_status_t
+stat_test_runs(uint8_t *data) {
+ uint8_t *data_end = data + STAT_TEST_DATA_LEN;
+ uint16_t runs[6] = { 0, 0, 0, 0, 0, 0 };
+ uint16_t gaps[6] = { 0, 0, 0, 0, 0, 0 };
+ uint16_t lo_value[6] = { 2315, 1114, 527, 240, 103, 103 };
+ uint16_t hi_value[6] = { 2685, 1386, 723, 384, 209, 209 };
+ int state = 0;
+ uint16_t mask;
+ int i;
+
+ /*
+ * the state variable holds the number of bits in the
+ * current run (or gap, if negative)
+ */
+
+ while (data < data_end) {
+
+ /* loop over the bits of this byte */
+ for (mask = 1; mask < 256; mask <<= 1) {
+ if (*data & mask) {
+
+ /* next bit is a one */
+ if (state > 0) {
+
+ /* prefix is a run, so increment the run-count */
+ state++;
+
+ /* check for long runs */
+ if (state > 25) {
+ debug_print(mod_stat, ">25 runs: %d", state);
+ return err_status_algo_fail;
+ }
+
+ } else if (state < 0) {
+
+ /* prefix is a gap */
+ if (state < -25) {
+ debug_print(mod_stat, ">25 gaps: %d", state);
+ return err_status_algo_fail; /* long-runs test failed */
+ }
+ if (state < -6) {
+ state = -6; /* group together gaps > 5 */
+ }
+ gaps[-1-state]++; /* increment gap count */
+ state = 1; /* set state at one set bit */
+ } else {
+
+ /* state is zero; this happens only at initialization */
+ state = 1;
+ }
+ } else {
+
+ /* next bit is a zero */
+ if (state > 0) {
+
+ /* prefix is a run */
+ if (state > 25) {
+ debug_print(mod_stat, ">25 runs (2): %d", state);
+ return err_status_algo_fail; /* long-runs test failed */
+ }
+ if (state > 6) {
+ state = 6; /* group together runs > 5 */
+ }
+ runs[state-1]++; /* increment run count */
+ state = -1; /* set state at one zero bit */
+ } else if (state < 0) {
+
+ /* prefix is a gap, so increment gap-count (decrement state) */
+ state--;
+
+ /* check for long gaps */
+ if (state < -25) {
+ debug_print(mod_stat, ">25 gaps (2): %d", state);
+ return err_status_algo_fail;
+ }
+
+ } else {
+
+ /* state is zero; this happens only at initialization */
+ state = -1;
+ }
+ }
+ }
+
+ /* move along to next octet */
+ data++;
+ }
+
+ if (mod_stat.on) {
+ debug_print(mod_stat, "runs test", NULL);
+ for (i=0; i < 6; i++)
+ debug_print(mod_stat, " runs[]: %d", runs[i]);
+ for (i=0; i < 6; i++)
+ debug_print(mod_stat, " gaps[]: %d", gaps[i]);
+ }
+
+ /* check run and gap counts against the fixed limits */
+ for (i=0; i < 6; i++)
+ if ( (runs[i] < lo_value[i] ) || (runs[i] > hi_value[i])
+ || (gaps[i] < lo_value[i] ) || (gaps[i] > hi_value[i]))
+ return err_status_algo_fail;
+
+
+ return err_status_ok;
+}
+
+
+/*
+ * the function stat_test_rand_source applys the FIPS-140-2 statistical
+ * tests to the random source defined by rs
+ *
+ */
+
+#define RAND_SRC_BUF_OCTETS 50 /* this value MUST divide 2500! */
+
+err_status_t
+stat_test_rand_source(rand_source_func_t get_rand_bytes) {
+ int i;
+ double poker;
+ uint8_t *data, *data_end;
+ uint16_t f[16] = {
+ 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0
+ };
+ uint8_t buffer[RAND_SRC_BUF_OCTETS];
+ err_status_t status;
+ int ones_count = 0;
+ uint16_t runs[6] = { 0, 0, 0, 0, 0, 0 };
+ uint16_t gaps[6] = { 0, 0, 0, 0, 0, 0 };
+ uint16_t lo_value[6] = { 2315, 1114, 527, 240, 103, 103 };
+ uint16_t hi_value[6] = { 2685, 1386, 723, 384, 209, 209 };
+ int state = 0;
+ uint16_t mask;
+
+ /* counters for monobit, poker, and runs tests are initialized above */
+
+ /* main loop: fill buffer, update counters for stat tests */
+ for (i=0; i < 2500; i+=RAND_SRC_BUF_OCTETS) {
+
+ /* fill data buffer */
+ status = get_rand_bytes(buffer, RAND_SRC_BUF_OCTETS);
+ if (status) {
+ debug_print(mod_stat, "couldn't get rand bytes: %d",status);
+ return status;
+ }
+
+#if 0
+ debug_print(mod_stat, "%s",
+ octet_string_hex_string(buffer, RAND_SRC_BUF_OCTETS));
+#endif
+
+ data = buffer;
+ data_end = data + RAND_SRC_BUF_OCTETS;
+ while (data < data_end) {
+
+ /* update monobit test counter */
+ ones_count += octet_get_weight(*data);
+
+ /* update poker test counters */
+ f[*data & 0x0f]++; /* increment freq. count for low nibble */
+ f[(*data) >> 4]++; /* increment freq. count for high nibble */
+
+ /* update runs test counters */
+ /* loop over the bits of this byte */
+ for (mask = 1; mask < 256; mask <<= 1) {
+ if (*data & mask) {
+
+ /* next bit is a one */
+ if (state > 0) {
+
+ /* prefix is a run, so increment the run-count */
+ state++;
+
+ /* check for long runs */
+ if (state > 25) {
+ debug_print(mod_stat, ">25 runs (3): %d", state);
+ return err_status_algo_fail;
+ }
+
+ } else if (state < 0) {
+
+ /* prefix is a gap */
+ if (state < -25) {
+ debug_print(mod_stat, ">25 gaps (3): %d", state);
+ return err_status_algo_fail; /* long-runs test failed */
+ }
+ if (state < -6) {
+ state = -6; /* group together gaps > 5 */
+ }
+ gaps[-1-state]++; /* increment gap count */
+ state = 1; /* set state at one set bit */
+ } else {
+
+ /* state is zero; this happens only at initialization */
+ state = 1;
+ }
+ } else {
+
+ /* next bit is a zero */
+ if (state > 0) {
+
+ /* prefix is a run */
+ if (state > 25) {
+ debug_print(mod_stat, ">25 runs (4): %d", state);
+ return err_status_algo_fail; /* long-runs test failed */
+ }
+ if (state > 6) {
+ state = 6; /* group together runs > 5 */
+ }
+ runs[state-1]++; /* increment run count */
+ state = -1; /* set state at one zero bit */
+ } else if (state < 0) {
+
+ /* prefix is a gap, so increment gap-count (decrement state) */
+ state--;
+
+ /* check for long gaps */
+ if (state < -25) {
+ debug_print(mod_stat, ">25 gaps (4): %d", state);
+ return err_status_algo_fail;
+ }
+
+ } else {
+
+ /* state is zero; this happens only at initialization */
+ state = -1;
+ }
+ }
+ }
+
+ /* advance data pointer */
+ data++;
+ }
+ }
+
+ /* check to see if test data is within bounds */
+
+ /* check monobit test data */
+
+ debug_print(mod_stat, "stat: bit count: %d", ones_count);
+
+ if ((ones_count < 9725) || (ones_count > 10275)) {
+ debug_print(mod_stat, "stat: failed monobit test %d", ones_count);
+ return err_status_algo_fail;
+ }
+
+ /* check poker test data */
+ poker = 0.0;
+ for (i=0; i < 16; i++)
+ poker += (double) f[i] * f[i];
+
+ poker *= (16.0 / 5000.0);
+ poker -= 5000.0;
+
+ debug_print(mod_stat, "stat: poker test: %f", poker);
+
+ if ((poker < 2.16) || (poker > 46.17)) {
+ debug_print(mod_stat, "stat: failed poker test", NULL);
+ return err_status_algo_fail;
+ }
+
+ /* check run and gap counts against the fixed limits */
+ for (i=0; i < 6; i++)
+ if ((runs[i] < lo_value[i] ) || (runs[i] > hi_value[i])
+ || (gaps[i] < lo_value[i] ) || (gaps[i] > hi_value[i])) {
+ debug_print(mod_stat, "stat: failed run/gap test", NULL);
+ return err_status_algo_fail;
+ }
+
+ debug_print(mod_stat, "passed random stat test", NULL);
+ return err_status_ok;
+}
+
+err_status_t
+stat_test_rand_source_with_repetition(rand_source_func_t source, unsigned num_trials) {
+ unsigned int i;
+ err_status_t err = err_status_algo_fail;
+
+ for (i=0; i < num_trials; i++) {
+ err = stat_test_rand_source(source);
+ if (err == err_status_ok) {
+ return err_status_ok;
+ }
+ debug_print(mod_stat, "failed stat test (try number %d)\n", i);
+ }
+
+ return err;
+}
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