I don't know about 30 years but AES-256-GCM has implementations in multiple programming languages, e.g. it can be decrypted dependency free in Node.js >= 10. If browsers were to drop support (unlikely imo), there should be multiple options for decryption provided one has access to a runtime supporting AES-256-GCM decrypt. An older WASM'd version of PHP or python may even work.
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 "$PWD:/app" -w /app node:10-alpine portable-secret-decrypt.js example-image.html"
When used with the Bart's drivers license it will create the decrypted file as decrypted.jpeg to the cwd.
I have no use for this myself but wrote a quick Node.js script which accepts an html file created by this tool and prints messages to stdout or saves a file to decrypted.ext: https://gist.github.com/andrewmackrodt/e6a5a2ea7b22d74102ba7... - it's dependency free (no npm install dependencies) and tested with Node.js 10 and above.
e.g. "docker run --rm -it -v "$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.