fix: reduce secret size to 160 bits

[st3iny]

Ref #1324 (comment)

We currently have a length of 160 * 5 bit = 800 bit which is a bit excessive.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b4b530a) 44.29% compared to head (7eb6dc4) 44.29%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1483   +/-   ##
=========================================
  Coverage     44.29%   44.29%           
  Complexity       99       99           
=========================================
  Files            19       19           
  Lines           298      298           
=========================================
  Hits            132      132           
  Misses          166      166           

Flag	Coverage Δ
unittests	44.29% <ø> (ø)

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