1. Open the html file in browser.
2. Drag and drop (or choose by file chooser) your text/image files.
3. Then add them to list.
4. Then set encryption key (password).
5. Then click 'Export html'.
6. Now, nobody can read your exported files without your password (encryption key).

Here is the link: https://waliul-islam-mondal.github.io/encrypted-file-vault-html/