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seen Jun 26 at 23:32

Jun
26
accepted Choose a random number that is different from a bunch of other secret numbers
Jun
26
comment Choose a random number that is different from a bunch of other secret numbers
@D.W.: thanks a lot, I took the paper from 1976 (?) and I wrote a "proof of concept" implementation of Pohlig-Hellman. I'll probably ask here later on another question related to how some of the parameters should be chosen for my use case.
Jun
25
comment Choose a random number that is different from a bunch of other secret numbers
@D.W.: Yes but I don't know which commutative encryption algo can be used here which doesn't require a TTP. I was under the impression that there were several encryption schemes which are commutative but which require a TTP to hold some private keys? (once again thanks for all the help and your patience)
Jun
25
comment Choose a random number that is different from a bunch of other secret numbers
@D.W: (and otus) yup this is very nice and I'm pretty sure that it solves my issue. Now as I don't want a TTP I'll need to find a way to implement that answer of yours without a TTP. I'll read the link you provided and then probably come up with another question!
Jun
25
comment Choose a random number that is different from a bunch of other secret numbers
(...) so once it's done the server can verify that everybody had been honest. It's not a problem that the server can verify, after the fact, that everybody has been fair (and hence know everyone's secret). But during the processus, the server must not know what is going on (or it could collude with a "voter"). I may come up with another question explaining what I'm trying to do but, basically, it's very close to the question I asked here :)
Jun
25
comment Choose a random number that is different from a bunch of other secret numbers
@D.W: (first thanks a lot for the edit)... It would be repeated only three times with the same secret value for the participants, so basically people would need to "agree" on three random numbers which do not clash with any secret. It's not peer-to-peer: there's a server but I don't want the server to act as a TTP. The secret values (and any "random" value needed, say for the crypto algo), are chosen using a CSPRNG seeded with a seed revealed to the server, by each participant, at the end of the processus. But a Non-malleable commitment (NMC) to that seed is published beforehand (...)
Jun
24
awarded  Commentator
Jun
24
comment Paillier can add and multiply, why is it only partially homomorphic?
@mikeazo: oh, ok... Didn't realize that: I've indeed been a bit confused by that little interactive demo. Makes a lot of sense. Thanks to both of you!
Jun
24
asked Paillier can add and multiply, why is it only partially homomorphic?
Jun
17
comment Choose a random number that is different from a bunch of other secret numbers
@RickyDemer: Basically I need the secrets to stay secrets only for a small amount of time but during that amount of time they need to be really secret. After a while everything can be published publicly. Which is convenient because is probably simplifies the implementation (for example by not requiring adding ZKNP etc.).
Jun
17
comment Choose a random number that is different from a bunch of other secret numbers
@mikeazo: x will be small, between 40 and 60 or something. The number of participant will not be very high, but high enough so that clashes are to be expected very often.
Jun
17
comment Choose a random number that is different from a bunch of other secret numbers
@RickyDemer: I mean that it's not necessary "inside" the crypto system because there are, in my use case, other means to verify that the participants have been honest after the "vote". For example picking the private/secret number and then participating in choosing a random public number is all done using a seed to a CSPRNG. A non-malleable commitment to that seed can be published (hence not revealing the seed) and then, say a few days later, everybody can release their seed. (if someone doesn't, the vote isn't valid).
Jun
17
revised Choose a random number that is different from a bunch of other secret numbers
added 18 characters in body
Jun
17
asked Choose a random number that is different from a bunch of other secret numbers
Apr
25
awarded  Editor
Apr
25
revised Are the RFC3526 MODP groups Schnorr groups?
deleted 1 character in body
Apr
25
accepted Are the RFC3526 MODP groups Schnorr groups?
Apr
25
comment Are the RFC3526 MODP groups Schnorr groups?
thanks, this really helps me a lot... I thought it was a Schnorr group, but I couldn't understand how the generator could possibly be 2.
Apr
25
asked Are the RFC3526 MODP groups Schnorr groups?
Mar
20
comment How does compression before encryption leak info about the input?
(*) (where there is hardly a paragraph which doesn't criticize Bruce Schneier's Applied Cryptography)