So one thing, it mentions that it is JS dependence free. How are you encrypting the files client side then?
If you are encrypting the files server side, then that is NOT E2E encryption.
If you are encrypting the files server side, then that is NOT E2E encryption.
There is a file called cipher.js with encrypt and decrypt functions https://github.com/countable-web/cryptsend/blob/develop/publ...