* Check openssl-compatibility of cfb/ofb cipher mapping
* investigate libcap as alternative to setuid
  - libcap-ng available on Arch, Fedora-34
  - libcap2 available on Arch, Fedora-34, Ubuntu-18.04
* document libgcrypt/libcryptsetup compatibility issues
* remove support for legacy /dev/loop/0 device nodes
* migrate unit-testing suite to CUnit
* add option for ingesting key-material via command-line
* run tests on 64-bit big-endian machines (e.g. sparc64)
* extend tests on --safetynet option
* add 'verbose' option?
* key-cache for multiple operations?
