I've been looking at the WebCrypto API. When combined with the File system API, it can be used to encrypt and store files on your device storage in what seems to be a pretty secure way.

A webapp has some clear vulnerabilities with the code being served over the web (so you shouldnt be using this for any serious purposes!).

Live demo: https://dim.positive-intentions.com/?path=%2Fstory%2Fusefs--encrypted-demo

Demo code: https://github.com/positive-intentions/dim/blob/staging/src/stories/05-Hooks-useFS.stories.js

IMPORTANT NOTES TO PREVENT MISLEADING

• this isnt a product. it provided for testing and demo.
• it isnt reviewed or audited.
• the "password encryption" is using a hardcoded password. id like to aim for a passwordless approach for this, but i havent considered it enough to discuss yet :)
• this isnt aimed to replace anything like veracrypt. just to show a comparison.
• this respository represents a webcomponent UI framework. while it holds some ideas i think are interesting, the ui framework seems like its going to be deprecated and i will be refactoring the functionality in favour of React.