KDiff3
https://apps.kde.org/en/kdiff3
This is a gist of ideas, notes etc. Some of them will be used for more detailed articles in my other blog.
Encrypt:
gpg --no-symkey-cache -c cd2.iso
Decrypt:
gpg --no-symkey-cache -o cd2.iso -d cd2.iso.gpg
unar -o temp -encoding cp866 my-old-arch.zip