Been spending some time looking at the design of Silent Payments, just from a crypto point of view. Overall I like it; the only wiggle room for attack I can find so far is if the spending key is somehow a key that itself previously existed and was used for something, which it never would be. I see basically no attacks that make sense, so far. If I have a complaint about the BIP, it's that it isn't as clear as it should be about what privacy guarantees it's claiming (though the common sense reading seems to be right; it should be explicit though). Obviously the way out there stuff, like inputs that are from MuSig2/FROST, or coinjoins, which are pointed at in the BIP, are very much uncharted territory and would be hard to get right, but for now I think that is just not going to happen. Anyway I'll keep looking.

#cryptography #bitcoin