This is a brilliant idea! Does Firefox accept feature proposals if they're fleshed out? My friend is an aspiring UX designer looking to build a portfolio, and I can write crude sample code.

Not so sure that's a good idea. This would prevent users to programmatically compare hashes, and it would be hard to display one next to the other to facilitate comparison. Keep in mind that it is relatively easy to create a file that matches the first and/or last N chars of a hash. And who checks the center of the hash? No, we have to have the browser compare the full hash and give a simple green light to the user. I don't have a proposition in terms of UX but it should be studied (should have been 15 years ago actually)

I was thinking the same thing, actually. I made a UX mockup this morning that I feel good about and was able to explain to my parents over brunch. I'll see if my friend wants to work on it.