I have no use for this myself but wrote a quick Node.js script which accepts an html file created by this tool and prints messages to stdout or saves a file to decrypted.ext: https://gist.github.com/andrewmackrodt/e6a5a2ea7b22d74102ba7... - it's dependency free (no npm install dependencies) and tested with Node.js 10 and above.
e.g. "docker run --rm -it -v "$PWD:/app" -w /app node:10-alpine portable-secret-decrypt.js example-image.html"
When used with the Bart's drivers license it will create the decrypted file as decrypted.jpeg to the cwd.
There’s more of a case for public-key stuff changing, but this doesn’t rely on anything public key.
No points will be awarded for citing jank that is a direct consequence of depending on proprietary, experimental, or non-standard stuff (like, "well, my Flash site worked in 2002, but now it doesn't").