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Minimum of two values with minimum knowledge (jlai.lu)

submitted 1 year ago by payasson@jlai.lu to c/cybersecurity@sh.itjust.works

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Hey! I program a lot but I'm not very good with cybersecurity and stuff, although I have a basic usage of GPG and asymetrical encryption.

My problem is:

Let's imagine that Alice (A) and Bob (B) each have a file with a number written in it.

Ideally, I'd like a program that A can run on her computer that would take the B file but encrypted, and output the minimum of the two values contained in A and B files.

But without any way for A to know what the number of B is, except if B value is the minimum, obviously.

Can someone help me with that? Thank you for reading!

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[–] Khanzarate@lemmy.world 1 points 1 year ago (1 children)

Possibly. I'm not a big crypto guy, but it's my understanding that any kind of transaction has a chance of being repeated. If there were a bad actor, and that bad actor used a VPN to swap identities, he could narrow this down considerably and weaken encryption. My code is as dumb as it gets, willing to consider 1 as a valid encryption key, but smarter code would be a lot more efficient.

On top of that, you wanted this minimum code to run on A's computer. If you do not trust A, then you've given a potential bad actor a program that could be decompiled to unencrypt your keys.

It sounds to me like in your current state, you need to trust A before you do this operation, and if you do, you can just share an unencrypted B.

[–] payasson@jlai.lu 0 points 1 year ago

Alright thank you for your reply, I'll think about it :) maybe having a vérification that can be done in any computer and any amount of time is just not possible for my use case