20,677 reputation
32574
bio website
location
age
visits member for 3 years, 3 months
seen Nov 10 at 4:37

Jun
18
answered Fiat–Shamir: why do r and s have to be smaller than n?
Jun
18
comment LFSR and Markov chain question
I don't understand in what sense the Berlekamp-Massey algorithm is an algorithm for "this problem" - what problem? Please try to be more precise. Berlekamp-Massey has nothing to do with Markov chains; it has to do with recovering the LFSR initial fill and feedback polynomial, given observations of its output. As far as your last question in your comment: for what task? what Markov chain formulation? It's impossible to say what resources are needed, if we don't know what the task is. Again, LFSRs are a deterministic process, so modelling it as a Markov chain is not very helpful.
Jun
18
comment LFSR and Markov chain question
I find this question unclear. What do you have in mind as the statespace of the Markov chain? If the state is the entire state of the LFSR, then of course there is a trivial Markov chain, since it is a deterministic process, but this does not seem likely to be useful. So what did you have in mind? Let me put it another way. Why do you ask this question? What's the motivation or context where you plan to use this? How will you evaluate or use answers? As it stands the question seems a bit on the open-ended/ill-defined end.
Jun
18
comment Length-preserving all-or-nothing transform
@fgrieu, actually, I think you have it backwards. For large size, it is straightforward (in the random oracle), as explained in the section "Theoretical perspective": use a cryptographic hash function as the F-function of a 6-round Feistel network. I actually think the more challenging case is to do it for small block size, not large block size.
Jun
18
revised Authenticated encryption without padding
added 189 characters in body
Jun
18
comment Authenticated encryption without padding
@RickyDemer, I've updated my answer to provide a construction that you might like better. If provable security is a goal, a better construction is likely to be $E_{k_2} \circ P \circ E_{k_1}$ where $P$ is a public random permutation and $E$ is a length-preserving encryption scheme. (Then even in the case where $E$ is merely xor with a constant, i.e., $E_k(x)=k \oplus x$, then it can still be proven to provide reasonable security, as this devolves to the Even-Mansour construction, which offers provable security guarantees.)
Jun
18
revised Authenticated encryption without padding
added 253 characters in body; added 466 characters in body
Jun
18
comment Can the premaster secret generated by SRP be used as a secure private key?
I recommend that you state the question you want answered in the body of the question.
Jun
18
comment SHA1 collision event probability after n iterations
Did you look at crypto.stackexchange.com/q/15068/351 ? (Did you remember to use search before asking?)
Jun
18
comment SHA1 collision event probability after n iterations
What do you think? What have you tried? Where did you get stuck? Where did you run into this question? What is the context/motivation for your question? This is not a site where you copy-paste your exercise and we do your exercise for you.
Jun
18
comment What are good combinations of public key algorithms or primitives for long term security?
I wouldn't recommend lattice-based methods at this point in time, for long-term security; they haven't been studied in as much detail as others. It wouldn't be shocking if someone discovered a new attack 10 years from now that breaks them significantly faster than we currently know how to.
Jun
18
revised Authenticated encryption without padding
added 219 characters in body
Jun
18
answered Length-preserving all-or-nothing transform
Jun
17
asked Length-preserving all-or-nothing transform
Jun
17
answered Authenticated encryption without padding
Jun
17
answered Non-commutitive and nonassociative algebraic structures in cryptography
Jun
12
answered Use of less than secure random numbers for 'a' during an SRP proof of password
Jun
11
comment Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
Please make sure to provide a specific technical question in the body of the question. The title is for, well, a title -- and does not replace to need to ask a specific question in the body of the question.
Jun
11
answered Comparing two values without revealing them
Jun
10
awarded  Custodian