Add current version of libSRTP from CVS.

libsrtp/crypto/math/stat.c

+/*
+ * 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;
+}