Well. Some time ago, I 've written small text editor which allows precisely that.
https://github.com/martinrotter/textosaurus
That feature is inspired by Geany.
OK, I changed the encryption to directly call "openssl" executable to do encryption/decryption stuff.
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I found this even better than linking against OpenSSL and calling EVP routines directly.
Follow this to see progress. I update my Qt toolchain to use openssl 1.1 and I will link against it and use it.
This will add dep to "openssl" on linux, but I guess its just okay, because (almost) everyone has it installed anyway.
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I will refactor my encryption logic and will use openssl where needed. Maybe I could also allow user to actually select what encryption method/cipher to use....
Please, test development Mac OS X build - https://github.com/martinrotter/textosaurus/wiki/Development-builds - and let me know if it works. It works fine in my virtualbox environment.
You can help me, and write documentation/simple-how-to for [Textosaurus](https://github.com/martinrotter/textosaurus/wiki/User-Manual). As you see, the manual is there, but it needs better structure, more content and updates. :)