Fix aes cipher portability issue

[jarevalo-ledger]

Description

Use types that are arch-independent to avoid 32/64 bit portability issues.
Some unit-tests running on x86 64-bit with sanitizers enabled fails.

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.47%. Comparing base (e21f13e) to head (9899632).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #668   +/-   ##
=======================================
  Coverage   60.47%   60.47%           
=======================================
  Files          12       12           
  Lines        1723     1723           
=======================================
  Hits         1042     1042           
  Misses        681      681           

Flag	Coverage Δ
unittests	60.47% <ø> (ø)

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