US export regulations require that any exported software package that encrypts data other than passwords (e.g., SSH, VPN, TLS) and uses nonstandard encryption algorithms to do so must disclose the algorithms to the federal govt. The penalties are pretty severe if you don’t.
‘Export’ includes simply putting your app on the Internet for free download.
So when NSA got hacked, all legal US algorithms [required to register them] might have been copied by the hackers then.
One thing, if we are ever reduced to going ‘old school’, here is a ‘poor man’s encryption’:
In the old fashioned text document [the very most basic one], I sometimes ‘auto-replace’ several misspelled words at once.
You can use that for the opposite purpose — to encrypt.
You could replace ‘a’ with xyz
You could replace ‘e’ with zzz
Every vowel with constanants and every constenant with vowels. And that’s just the simplist way of doing it.
You could have multiple translations for each ‘a’, such as either xyz or yyy.
Or you could replace one letter with another single letter, but that takes more work.
Then reverse the process with auto-correct.
A lot of work unfortunately.