[Cryptography] Dieharder & symmetric cryptosystems

[Michel Arboi]

Hello,

Sorry for awakening an old thread but it appears that miscellaneous changes
to /dev/random or /dev/urandom during the last couple of years did not
fundamentally fix what I noticed in 2019, supposing that this apparent
weakness needed fixing.
(In summary, some WEAK results appeared very often on some specific tests
with the /dev/urandom generator, while they never appeared with
/dev/random, or very rarely)
The main change is that /dev/random is now "as weak" as /dev/urandom,
probably because of this:
https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.6-Random-Rework

Considering that the old /dev/random or other PRNG do not exhibit this
behaviour, I suspect some kind of weakness here. I still could not find any
explanation.

$ dieharder -a -g 500
#=============================================================================#
#            dieharder version 3.31.1 Copyright 2003 Robert G. Brown
   #
#=============================================================================#
   rng_name    |rands/second|   Seed   |
    /dev/random|  1.47e+07  |  97623993|
#=============================================================================#
        test_name   |ntup| tsamples |psamples|  p-value |Assessment
#=============================================================================#
   diehard_birthdays|   0|       100|     100|0.98853103|  PASSED
[snip]
          sts_serial|  10|    100000|     100|0.83110218|  PASSED
          sts_serial|  10|    100000|     100|0.99559169|   WEAK
<-------------- here
          sts_serial|  11|    100000|     100|0.98425140|  PASSED
[snip]
          sts_serial|  15|    100000|     100|0.99501524|   WEAK
[snip]
      rgb_lagged_sum|  14|   1000000|     100|0.47229376|  PASSED
      rgb_lagged_sum|  15|   1000000|     100|0.99950974|   WEAK
[snip]
Preparing to run test 209.  ntuple = 0
        dab_monobit2|  12|  65000000|       1|0.25934883|  PASSED
$ dieharder -a -g 501
#=============================================================================#
#            dieharder version 3.31.1 Copyright 2003 Robert G. Brown
   #
#=============================================================================#
   rng_name    |rands/second|   Seed   |
   /dev/urandom|  7.84e+06  |3770177091|
#=============================================================================#
        test_name   |ntup| tsamples |psamples|  p-value |Assessment
#=============================================================================#
   diehard_birthdays|   0|       100|     100|0.48144031|  PASSED
[snip]
        diehard_sums|   0|       100|     100|0.00896211|  PASSED
        diehard_runs|   0|    100000|     100|0.00135805|   WEAK
        diehard_runs|   0|    100000|     100|0.32971394|  PASSED
[snip]
        diehard_runs|   0|    100000|     100|0.00135805|   WEAK
[snip]
          sts_serial|   3|    100000|     100|0.00381696|   WEAK
[snip]
          sts_serial|  13|    100000|     100|0.99985868|   WEAK
[snip]
      rgb_lagged_sum|  22|   1000000|     100|0.00401025|   WEAK
[snip]
$
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