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seen Nov 24 at 17:24

Feb
5
answered Practical (and secure) PRGs
Feb
4
answered Hill cipher, unknown letter value
Feb
4
comment Hill cipher is not perfectly secure
@Valtteri, well done!
Feb
4
answered Hill cipher is not perfectly secure
Feb
4
comment Game with symmetric key
What do you think? What have you tried? We prefer you to make an effort on your own before asking. This is a nice exercise, but we're not here to solve your exercises for you -- on the other hand, if you have a specific question about a specific aspect of your attempt at a solution, that might be more suitable for this site.
Feb
3
revised Homomorphic encryption for vector addition
Fix typos pointed out by figlesquidge.
Feb
2
revised Homomorphic encryption for vector addition
added 3715 characters in body
Feb
2
answered Homomorphic encryption for vector addition
Jan
31
comment Addition-only PHE in F#
@uosɐſ, that's a different question, so it should be posted separately as a separate question. One question per question, please: this is not a discussion forum, so it's important to keep things focused. I think I might be able to propose some candidate solutions, but I don't want to post it here.
Jan
31
answered Addition-only PHE in F#
Jan
30
comment Efficient Robust Private Set Intersection Questions
user11706, The etiquette on this site is to edit the question to include this information into the question. When asked for clarification, don't just add a comment; edit the question to make it self-contained. People shouldn't need to read the comment thread to understand everything needed to understand the question. Looks like figlesquidge has done that for you, but you should do it yourself in the future.
Jan
30
awarded  Deputy
Jan
30
awarded  random-number-generator
Jan
30
comment Efficient Robust Private Set Intersection Questions
Section 3.4 of what? Step 7 of what? I have no idea what you are referring to. What have you tried? Do you understand what it means to work in a finite field? I suggest you go back and review the basics, like finite fields and modular arithmetics.
Jan
29
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
@Angela, ahh, good question! Probably the answer will depend on the formulas or how they were generated; in some cases, yes, knowing the explicit formulas will allow you to invert them -- but not always. I don't know if it is possible to give a general answer.
Jan
29
answered Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
Jan
29
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
Oh, also: you're going to need to give us some way to get some element(s) of $S$ to get started, otherwise we have no way to do anything in $S$ (we don't have anything we can apply the $\Delta$ or $*$ operations to). So what can we do? Can we generate a random element of $S$? If yes, are we told what element of $R$ it corresponds to?
Jan
29
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
Finally, I'll comment that a ring is an algebraic structure that has more than just addition and multiplication as operations. It also has negation (the inverse for addition) and inversion (the inverse for multiplication) maps, i.e., the maps $x \mapsto -x$ and $x \mapsto x^{-1}$. Are we given the ability to apply these maps to elements of $S$ of our choice? The natural answer would be "yes" (but in that case the question becomes trivial). If the answer in your situation is "no", why not? What is the motivation for the question?
Jan
29
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
Also I think you need to be more careful about how elements of $S$ are represented, and what it means to be given an element of $S$. Presumably what you mean is that there is some way of representing an element of $S$, and when we are given an element of $S$, you mean we are given the corresponding bit string. OK, fine. So, what do we know about the representation? What are we given? Do we know the map from elements of $S$ to bit strings, or the reverse map? I suggest you take more care in your question to distinguish an element from the representation of that element.
Jan
29
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
Angela, what does it mean to say you are "given the elements of $S$"? There are exponentially many elements of $S$, so we cannot be literally given a list of all elements of $S$ (represented somehow) -- that wouldn't make sense. So what do you mean? P.S. Make sure you edit your question to make it self-contained and comprehensible without reading the comment thread. This is not a discussion forum. We expect you to spend serious effort to craft a well-posed, well-explained problem statement.