Comment by econ
21 days ago
I like it. Perhaps you can use a weird idea of mine.
You can discard/modify part of a password before sending it to your backend. Then, when you log in the server has to brute force the missing part.
One could extend this with security questions like how many children pets and cars you own. What color was your car in 2024. Use that data to aid brute forcing.
The goal would be to be able to decrypt with fewer than 5 shards but make it as computation heavy as you like. If no one remembers the pink car it will take x hours longer.
This makes little sense, IMO. Information is information. There is no difference between this and just having a short/simple passphrase with the PKBDF iterations turned very high. You might as well shard secrets using Shamir and encode it via a modified version of BIP32 words.
I'm no crypto expert, just fooling around.
The security questions are like extra shares of lower value.
My mental model is something like burying the password in your 100x100 yard. You give one friend the X and a different friend the Y coordinates both rounded down to a multiple of 10 meters. The security questions can be added to the X and Y coordinates.
X = 30 + 2 + 3 + 1
Y = ?? + 3 + 5 + 1
You only have to dig 9 holes now.
That is a neat take on "key strengthening", or "peppering":
https://crypto.stackexchange.com/questions/20578/definition-...
That sounds like a roundabout way of doing security questions... https://security.stackexchange.com/questions/186297/do-secur...
ohhhh that's brutal haha! for context my app runs entirely clientside, but I get it, it's an interesting idea...
I wonder if they even need a file. They could pick some question and type their secret into the app, something like the name of their first date etc
If you are to hand out files maybe it is wonderful to write them a letter that serves as their shard? They might actually store it some place safe and it wouldn't scream I'M A SECRET!