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Additional Testing Of The rtl-sdr Dongle As A HWRNG

A couple days ago, I put up a post about using the Realtek SDR dongles as a hardware true random number generator. I only tested the randomness of a 512 MB file. I thought this time, I would but a bit more stock into it. In this case, I let it run for a while, until it was 1.8 GB in size. Interestingly enough, it stopped getting bigger after that point. Not sure why. However, I ran more tests on that 1.8 GB file. Creating this file took its time:

$ tail -f /run/rtl_entropy.fifo | dd of=random.img iflag=fullblock
3554130+0 records in
3554130+0 records out
1819714560 bytes (1.8 GB) copied, 3897.22 s, 467 kB/s

This filled up a bit faster than I had previously tested, going at a clip of about 3.826 Mbps.

Now it was time for the testing:

$ ent random.img
Entropy = 8.000000 bits per byte.

Optimum compression would reduce the size
of this 1819714560 byte file by 0 percent.

Chi square distribution for 1819714560 samples is 246.86, and randomly
would exceed this value 63.11 percent of the times.

Arithmetic mean value of data bytes is 127.4990 (127.5 = random).
Monte Carlo value for Pi is 3.141611317 (error 0.00 percent).
Serial correlation coefficient is 0.000013 (totally uncorrelated = 0.0).

It passes with flying colors on entropy estimation, compression, chi-square distributions, arithmetic mean, the Monte Carlo estimation for Pi, and serial correlation. Testing further, I ran it through the FIPS 140-2 tests:

$ rngtest < random.img
rngtest 2-unofficial-mt.14
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: entropy source exhausted!
rngtest: bits received from input: 14557716480
rngtest: FIPS 140-2 successes: 727288
rngtest: FIPS 140-2 failures: 597
rngtest: FIPS 140-2(2001-10-10) Monobit: 99
rngtest: FIPS 140-2(2001-10-10) Poker: 57
rngtest: FIPS 140-2(2001-10-10) Runs: 210
rngtest: FIPS 140-2(2001-10-10) Long run: 233
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=114.212; avg=6626.942; max=9536.743)Mibits/s
rngtest: FIPS tests speed: (min=61.133; avg=147.877; max=151.377)Mibits/s
rngtest: Program run time: 96034230 microseconds
You have new mail.
$ echo $?
1

Finally, the beast of beasts, I ran it through every Dieharder test. This took some time to complete. Here is a listing of the tests that it went through:

$ dieharder -l
#=============================================================================#
#            dieharder version 3.31.1 Copyright 2003 Robert G. Brown          #
#=============================================================================#
Installed dieharder tests:
 Test Number	                     Test Name	              Test Reliability
===============================================================================
  -d 0  	                  Diehard Birthdays Test	      Good
  -d 1  	                     Diehard OPERM5 Test	      Good
  -d 2  	          Diehard 32x32 Binary Rank Test	      Good
  -d 3  	            Diehard 6x8 Binary Rank Test	      Good
  -d 4  	                  Diehard Bitstream Test	      Good
  -d 5  	                            Diehard OPSO	   Suspect
  -d 6  	                       Diehard OQSO Test	   Suspect
  -d 7  	                        Diehard DNA Test	   Suspect
  -d 8  	      Diehard Count the 1s (stream) Test	      Good
  -d 9  	        Diehard Count the 1s Test (byte)	      Good
  -d 10  	                Diehard Parking Lot Test	      Good
  -d 11  	Diehard Minimum Distance (2d Circle) Test	      Good
  -d 12  	Diehard 3d Sphere (Minimum Distance) Test	      Good
  -d 13  	                    Diehard Squeeze Test	      Good
  -d 14  	                       Diehard Sums Test	Do Not Use
  -d 15  	                       Diehard Runs Test	      Good
  -d 16  	                      Diehard Craps Test	      Good
  -d 17  	            Marsaglia and Tsang GCD Test	      Good
  -d 100  	                        STS Monobit Test	      Good
  -d 101  	                           STS Runs Test	      Good
  -d 102  	           STS Serial Test (Generalized)	      Good
  -d 200  	               RGB Bit Distribution Test	      Good
  -d 201  	   RGB Generalized Minimum Distance Test	      Good
  -d 202  	                   RGB Permutations Test	      Good
  -d 203  	                     RGB Lagged Sum Test	      Good
  -d 204  	        RGB Kolmogorov-Smirnov Test Test	      Good
  -d 205  	                       Byte Distribution	      Good
  -d 206  	                                 DAB DCT	      Good
  -d 207  	                      DAB Fill Tree Test	      Good
  -d 208  	                    DAB Fill Tree 2 Test	      Good
  -d 209  	                      DAB Monobit 2 Test	      Good

So here are the results:

 $ dieharder -a < random.img
#=============================================================================#
#            dieharder version 3.31.1 Copyright 2003 Robert G. Brown          #
#=============================================================================#
   rng_name    |rands/second|   Seed   |
        mt19937|  1.25e+08  | 169223456|
#=============================================================================#
        test_name   |ntup| tsamples |psamples|  p-value |Assessment
#=============================================================================#
   diehard_birthdays|   0|       100|     100|0.91937112|  PASSED  
      diehard_operm5|   0|   1000000|     100|0.77213572|  PASSED  
  diehard_rank_32x32|   0|     40000|     100|0.04709503|  PASSED  
    diehard_rank_6x8|   0|    100000|     100|0.93031877|  PASSED  
   diehard_bitstream|   0|   2097152|     100|0.12183977|  PASSED  
        diehard_opso|   0|   2097152|     100|0.96023625|  PASSED  
        diehard_oqso|   0|   2097152|     100|0.61237304|  PASSED  
         diehard_dna|   0|   2097152|     100|0.66045974|  PASSED  
diehard_count_1s_str|   0|    256000|     100|0.16999968|  PASSED  
diehard_count_1s_byt|   0|    256000|     100|0.00992823|  PASSED  
 diehard_parking_lot|   0|     12000|     100|0.69592283|  PASSED  
    diehard_2dsphere|   2|      8000|     100|0.95358410|  PASSED  
    diehard_3dsphere|   3|      4000|     100|0.89028448|  PASSED  
     diehard_squeeze|   0|    100000|     100|0.81631204|  PASSED  
        diehard_sums|   0|       100|     100|0.03559934|  PASSED  
        diehard_runs|   0|    100000|     100|0.75027140|  PASSED  
        diehard_runs|   0|    100000|     100|0.43076351|  PASSED  
       diehard_craps|   0|    200000|     100|0.57749359|  PASSED  
       diehard_craps|   0|    200000|     100|0.00599436|  PASSED  
 marsaglia_tsang_gcd|   0|  10000000|     100|0.60121369|  PASSED  
 marsaglia_tsang_gcd|   0|  10000000|     100|0.04254338|  PASSED  
         sts_monobit|   1|    100000|     100|0.94352358|  PASSED  
            sts_runs|   2|    100000|     100|0.77549833|  PASSED  
          sts_serial|   1|    100000|     100|0.46198961|  PASSED  
          sts_serial|   2|    100000|     100|0.46002706|  PASSED  
          sts_serial|   3|    100000|     100|0.73076110|  PASSED  
          sts_serial|   3|    100000|     100|0.90967100|  PASSED  
          sts_serial|   4|    100000|     100|0.32002297|  PASSED  
          sts_serial|   4|    100000|     100|0.07478887|  PASSED  
          sts_serial|   5|    100000|     100|0.27486408|  PASSED  
          sts_serial|   5|    100000|     100|0.57409336|  PASSED  
          sts_serial|   6|    100000|     100|0.05095556|  PASSED  
          sts_serial|   6|    100000|     100|0.06341272|  PASSED  
          sts_serial|   7|    100000|     100|0.00941089|  PASSED  
          sts_serial|   7|    100000|     100|0.53679805|  PASSED  
          sts_serial|   8|    100000|     100|0.00122125|   WEAK   
          sts_serial|   8|    100000|     100|0.16239101|  PASSED  
          sts_serial|   9|    100000|     100|0.24007712|  PASSED  
          sts_serial|   9|    100000|     100|0.02659941|  PASSED  
          sts_serial|  10|    100000|     100|0.64616186|  PASSED  
          sts_serial|  10|    100000|     100|0.78783799|  PASSED  
          sts_serial|  11|    100000|     100|0.77618602|  PASSED  
          sts_serial|  11|    100000|     100|0.33875893|  PASSED  
          sts_serial|  12|    100000|     100|0.50423715|  PASSED  
          sts_serial|  12|    100000|     100|0.77528158|  PASSED  
          sts_serial|  13|    100000|     100|0.57625144|  PASSED  
          sts_serial|  13|    100000|     100|0.73422196|  PASSED  
          sts_serial|  14|    100000|     100|0.40891605|  PASSED  
          sts_serial|  14|    100000|     100|0.48542772|  PASSED  
          sts_serial|  15|    100000|     100|0.67319390|  PASSED  
          sts_serial|  15|    100000|     100|0.74730027|  PASSED  
          sts_serial|  16|    100000|     100|0.67519158|  PASSED  
          sts_serial|  16|    100000|     100|0.73171087|  PASSED  
         rgb_bitdist|   1|    100000|     100|0.87216594|  PASSED  
         rgb_bitdist|   2|    100000|     100|0.18831902|  PASSED  
         rgb_bitdist|   3|    100000|     100|0.16757216|  PASSED  
         rgb_bitdist|   4|    100000|     100|0.05327115|  PASSED  
         rgb_bitdist|   5|    100000|     100|0.75278396|  PASSED  
         rgb_bitdist|   6|    100000|     100|0.64749144|  PASSED  
         rgb_bitdist|   7|    100000|     100|0.20311557|  PASSED  
         rgb_bitdist|   8|    100000|     100|0.39994123|  PASSED  
         rgb_bitdist|   9|    100000|     100|0.52805289|  PASSED  
         rgb_bitdist|  10|    100000|     100|0.96091722|  PASSED  
         rgb_bitdist|  11|    100000|     100|0.97794399|  PASSED  
         rgb_bitdist|  12|    100000|     100|0.75009561|  PASSED  
rgb_minimum_distance|   2|     10000|    1000|0.58923867|  PASSED  
rgb_minimum_distance|   3|     10000|    1000|0.54294743|  PASSED  
rgb_minimum_distance|   4|     10000|    1000|0.59446131|  PASSED  
rgb_minimum_distance|   5|     10000|    1000|0.00047025|   WEAK   
    rgb_permutations|   2|    100000|     100|0.89040191|  PASSED  
    rgb_permutations|   3|    100000|     100|0.47917416|  PASSED  
    rgb_permutations|   4|    100000|     100|0.30964668|  PASSED  
    rgb_permutations|   5|    100000|     100|0.70217495|  PASSED  
      rgb_lagged_sum|   0|   1000000|     100|0.12796648|  PASSED  
      rgb_lagged_sum|   1|   1000000|     100|0.15077254|  PASSED  
      rgb_lagged_sum|   2|   1000000|     100|0.31141471|  PASSED  
      rgb_lagged_sum|   3|   1000000|     100|0.94974697|  PASSED  
      rgb_lagged_sum|   4|   1000000|     100|0.99256987|  PASSED  
      rgb_lagged_sum|   5|   1000000|     100|0.67854004|  PASSED  
      rgb_lagged_sum|   6|   1000000|     100|0.08600877|  PASSED  
      rgb_lagged_sum|   7|   1000000|     100|0.91633363|  PASSED  
      rgb_lagged_sum|   8|   1000000|     100|0.06794590|  PASSED  
      rgb_lagged_sum|   9|   1000000|     100|0.59024027|  PASSED  
      rgb_lagged_sum|  10|   1000000|     100|0.59285975|  PASSED  
      rgb_lagged_sum|  11|   1000000|     100|0.87178336|  PASSED  
      rgb_lagged_sum|  12|   1000000|     100|0.63401541|  PASSED  
      rgb_lagged_sum|  13|   1000000|     100|0.47202172|  PASSED  
      rgb_lagged_sum|  14|   1000000|     100|0.34616699|  PASSED  
      rgb_lagged_sum|  15|   1000000|     100|0.97221211|  PASSED  
      rgb_lagged_sum|  16|   1000000|     100|0.95576739|  PASSED  
      rgb_lagged_sum|  17|   1000000|     100|0.32367098|  PASSED  
      rgb_lagged_sum|  18|   1000000|     100|0.92792046|  PASSED  
      rgb_lagged_sum|  19|   1000000|     100|0.58128429|  PASSED  
      rgb_lagged_sum|  20|   1000000|     100|0.78197001|  PASSED  
      rgb_lagged_sum|  21|   1000000|     100|0.86068846|  PASSED  
      rgb_lagged_sum|  22|   1000000|     100|0.22496908|  PASSED  
      rgb_lagged_sum|  23|   1000000|     100|0.52387665|  PASSED  
      rgb_lagged_sum|  24|   1000000|     100|0.52748770|  PASSED  
      rgb_lagged_sum|  25|   1000000|     100|0.96442902|  PASSED  
      rgb_lagged_sum|  26|   1000000|     100|0.51298847|  PASSED  
      rgb_lagged_sum|  27|   1000000|     100|0.99123470|  PASSED  
      rgb_lagged_sum|  28|   1000000|     100|0.69774674|  PASSED  
      rgb_lagged_sum|  29|   1000000|     100|0.83646714|  PASSED  
      rgb_lagged_sum|  30|   1000000|     100|0.98573851|  PASSED  
      rgb_lagged_sum|  31|   1000000|     100|0.23580471|  PASSED  
      rgb_lagged_sum|  32|   1000000|     100|0.19150884|  PASSED  
     rgb_kstest_test|   0|     10000|    1000|0.67771558|  PASSED  
     dab_bytedistrib|   0|  51200000|       1|0.07152541|  PASSED  
             dab_dct| 256|     50000|       1|0.53841656|  PASSED  
Preparing to run test 207.  ntuple = 0
        dab_filltree|  32|  15000000|       1|0.09092747|  PASSED  
        dab_filltree|  32|  15000000|       1|0.83382174|  PASSED  
Preparing to run test 208.  ntuple = 0
       dab_filltree2|   0|   5000000|       1|0.37363586|  PASSED  
       dab_filltree2|   1|   5000000|       1|0.26890999|  PASSED  
Preparing to run test 209.  ntuple = 0
        dab_monobit2|  12|  65000000|       1|0.80810458|  PASSED  

I don't have an image to look at to visually verify that there are no obvious patterns. At 1.8 GB, I feel that it would be just a bit too unwieldy anyway. So, I'll need to trust the previous tests for randomness that the data really is random. After these 3 series of tests, I can only conclude that using a Realtek SDR as a HWRNG will generate as "true random" data as you can hope for.

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