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Jul
28
comment Words having weight near to minimum distance
OK, that's a fine question -- but it's not what your question currently says. So, edit your question to say that. List the requirements you want the code to have, and ask whether such a code exists.
Jul
28
comment Words having weight near to minimum distance
That doesn't help. What do you mean by "we know its construction"? We know the binary matrix $H$; that is a construction of the code. I think my earlier question stands. If you're asking "Does there exist a class of codes for which the problem is easy" then the answer is a trivial but uninteresting yes, and that's probably not what you really intended to ask. If the question is "Please describe all classes of codes for which the problem is easy", then it's too broad for this site. In any case, you need to be more explicit about what the question is.
Jul
28
comment Reduction to cdp,dl or cdh?
You didn't answer my questions.
Jul
28
comment Words having weight near to minimum distance
I'm not sure what you're asking. What do you mean by "the code is known/unknown"? It's part of the input, so it's certainly known to the algorithm. Do you mean, for a specific class of codes, is this problem still NP-hard? Please edit the question to clarify. If so, it'll depend on the class of codes. What class of codes did you have in mind? And what research have you done? Have you done a literature search?
Jul
28
comment Reduction to cdp,dl or cdh?
Where does $x$ come from? Is it random? Is it fixed? (so it's a constant like, say, 7)? Is it part of the input? What do you mean by "distinguishing encodings of $x$"? What are your thoughts? What have you tried?
Jul
27
comment Fast attack on approximate GCD problem?
OK. There are lattice-based algorithms for this problem (Cohn & Heninger), continued fraction based methods, and more. Have you done a literature search? Did you check Google Scholar? I think you'll find some stuff there -- you might want to do a literature search, compile everything you find, then answer your own question with a summary of the known attacks.
Jul
24
comment Terminology: differences between the terms “pre-master secret”, “master secret”, “private key”, and “shared secret”?
Pre-master secret: tools.ietf.org/html/rfc5246#page-58. Computation of master secret, and how it differs from pre-master secret: tools.ietf.org/html/rfc5246#page-64. The session keys are defined and used in the record layer: tools.ietf.org/html/rfc5246#page-16. If you want to know how TLS works, reading the entire spec is a great exercise!
Jul
24
comment Terminology: differences between the terms “pre-master secret”, “master secret”, “private key”, and “shared secret”?
What research have you done? Have you read the TLS spec? The official spec would be the obvious place to check, and I believe it's all defined in there. Reading questions here isn't a substitute for checking the primary sources.
Jul
18
comment Why does “2xAES-256” provide “99.99%” security strength whereas “1xAES-128” provides “40%”?
I'm voting to close this question as off-topic because it's asking a particular company obtained their particular marketing claims. Only that company knows how they constructed their marketing and where they got those numbers from. This site is for technical questions that admit an objectively correct answer.
Jul
12
comment How broken is a xor of two multiply with carry generators?
@Charphacy, thanks for your comments. However, I'm afraid that fast non-crypto-strength PRNGs for non-crypto applications are off-topic for this site -- I'm sure it's a fascinating topic, but this site probably isn't the right place for it. See crypto.stackexchange.com/help/on-topic.
Jul
10
comment How hard is it to recover $p$ if I can get $h(p) \oplus h(p^*) \oplus r$ and $h(r)$?
What's the motivation for this question? What's the context in which you ran into it? It seems rather strange: I can't imagine why such a system would return such a value to the attacker -- and I especially can't imagine a setting where the attacker would learn this value but wouldn't know $p^*$. What does that even mean? What's the distribution of $p^*$? What do you mean by a guess? Without that, I don't see how this question can be answered.
Jul
3
comment How broken is a xor of two multiply with carry generators?
3. The question is not well-defined. There are many variants of MWC generators. The security of the scheme might depend upon what variant you choose and what parameters you choose (e.g., the lag, the base, the multiplier, the initial carry). Can you provide a complete specification of your proposed scheme with all parameters specified? What size is the seed for each MWC generator?
Jul
3
comment How broken is a xor of two multiply with carry generators?
1. Can you provide any motivation for this question? Why should we care? I could generate endless number of variants of a question that take the form "Consider the following rather-dubious PRNG that's probably not secure and hopefully no one uses; just how badly broken is it?", but I don't know if that'd be useful to the world at large. 2. What research have you done? What effort have you made? What is the best attack you can find on this cipher? We expect you to make a significant effort before asking here, and to show us what research/attempts you've made.
Jul
3
comment I hashed my bag and in it I put… “Is there a hash for unordered items?”
In addition to the excellent answer below based on Merkle hash trees, you can also take a look at crypto.stackexchange.com/q/11420/351 and crypto.stackexchange.com/q/6497/351 and crypto.stackexchange.com/a/489/351 (H(sort(H(x),H(y),..))) and crypto.stackexchange.com/q/17935/351.
Jul
3
comment I hashed my bag and in it I put… “Is there a hash for unordered items?”
possible duplicate of Hash of multiset of values, which lets me compute the hash of the union
Jun
29
comment What is a “lattice” in cryptography?
What research/self-study have you done? We expect you to do some research on your own before asking. See crypto.stackexchange.com/help/how-to-ask. Your question is covered in many standard places, e.g., textbooks and Wikipedia. If your question is answered in the obvious place on Wikipedia, you probably haven't done enough research before asking.
Jun
22
comment Which symmetric cipher is best for studying?
Study, for what purposes? What are your study goals? What do you want to learn? This will greatly affect the answer. (Also, you seem to have an implicit premise that the best way to learn whatever it is you want to learn is by devoting your time to studying a single modern symmetric cipher. I think there's a good chance that premise is not accurate.)
Jun
17
comment Brute-force attack given multiple hash prefixes
There's no "big question" here. SHA-1 is almost certainly such a function -- if it wasn't, it would be horribly broken, and we probably would have noticed this deviation from random from now. So from the perspective of an attacker, yes, an attack can absolutely treat SHA-1 in this way. As a result, the bottom line is: 2 candidates are enough to filter down to the true secret. Universal hash functions are a distraction, and the last paragraph introduces uncertainty that doesn't really exist in practice.
Jun
7
comment Is it possible to choose which point will have the public key of a given Elliptic Curve?
What are you free to choose? Are you free to choose the generator? The definition of the curve? (i.e., the equation defining the curve) Or are those fixed? Please edit your question to clarify -- as it stands it can't be answered definitively, as the answer depends on those constraints.
Jun
4
comment How do we know a cryptographic primitive won't fail suddenly?
You can't be sure. You can't be sure any of them are secure, and you can't be sure you'll have advance warning of a break. See What's the mathematical model behind the security claims of symmetric ciphers and digest algorithms? and How to prove the security of the PRNG? for more.