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May
15
comment Is there a way to do fair exchange between two parties who don't trust each other?
"there has been done very little research in this area" - Not true. There have been tons of papers written on fair exchange protocols. (Google Scholar turns up over 100.) Have you done a literature search? You should.
May
14
comment CSPRNG in JavaScript using Audio and Video
"Which mode should I use for AES encryption?" - None of them. Encryption is the wrong primitive here. You want to use a cryptographic PRNG (which may involve hashing low-entropy data, so it might use a hash function); but you really don't want to build one of those yourself, you're better off using a carefully-vetted scheme and implementation built by someone who knows this stuff cold.
May
14
comment CSPRNG in JavaScript using Audio and Video
"Gathering binary data from a webcam/microphone" - This is not a good solution for a web application (written in Javascript, and running in the browser). First, only modern browsers support access to the webcam/microphone from Javascript (without using Flash), but if the user has a modern browser, it'll probably support window.crypto.getRandomValues() too, and in that case you're better off using the latter. Second, even if the browser allows access to webcam/microphone, it'll prompt the user to grant access. Users may be reluctant to grant your website that access; then whatcha gonna do?
May
13
comment Is there a way to do fair exchange between two parties who don't trust each other?
I think you know this, but just to be very explicit: The protocol in this answer doesn't meet the requirement of the original question. If Alice is malicious, she can arrange to learn Bob's message without revealing her own message.
May
13
comment Why is the following RSA PRNG cryptographically secure?
It's not cryptographically secure. Why do you think it is? Where did that premise come from? You might want to investigate where you got that assumption from -- that might help you answer your question yourself.
May
12
comment Combining LFSRs for Stream Ciphers: Why do we need high non-linearity?
@DilipSarwate, absolutely, great point! My answer keeps it simple and assumes the feedback polynomial / tap locations are known. Yes, if the feedback polynomial is not known, then twice as many bits of known keystream are needed, and more sophisticated methods are needed. Thank you for pointing this out!
May
10
comment How to do a literature search
I'm hoping this may generate a good reference question that will be generally applicable, so when people have questions about how to find research papers on topic X, we can refer them to this question for a good starting point.
May
10
comment random number generator 10-side dice alternative
I don't understand. What problem are you trying to solve, that dice don't solve? Do you just want something different for the sake of being different? Or do you have some specific metric that you're trying to optimize, where you want something that's better than dice on that metric? If the latter, can you be more explicit about what that metric is?
May
10
comment Cryptography based upon neural networks
Jager, do you know how to do a literature search? If not, I suggest that you ask a question about how to do a literature search/review; that will be broadly useful to others. Alternatively, if you do know how to do a literature search, your first step should be to conduct a literature review first, to find all the research you can that seems related to this subject, and then read the papers you've found. That should help you figure out whether you have a more concrete, answerable question about this subject.
May
10
comment Trying to better understand the failure of the Index Calculus for ECDLP
What's the question again? I see some reasonable statements, but I'm having a hard time understanding what is the question you want an answer to. Can you try to formulate a concrete, answerable question?
May
10
comment Cryptography based upon neural networks
This site is not a good place for general, open-ended discussions ("I would like you to express your opinions about [broad subject]"). Instead, it is for concrete questions with a correct answer. Please read the FAQ before asking questions.
May
10
comment Security of Salsa20 with some known plaintext?
It depends. There are many details. For instance, if you use a key derived from a password, it'll likely be insecure. If you fail to use authenticated encryption (e.g., a MAC), it'll be susceptible to chosen-ciphertext attacks. There are a number of ways to go wrong. Usually you shouldn't try to encrypt in this way; instead, you should use an existing, well-vetted scheme/software, like GnuPG
May
9
comment What kind of adversary is the cloud?
It might be silly for Amazon to attack their customers, but that doesn't mean the semi-honest threat model is a good one for treating Amazon's cloud services. See my answer for explanations/details on why.
May
8
comment Increased CRC collision probability when adding bits to input message
I don't understand what this has to do with cryptography. A CRC is not cryptographically secure.
May
8
comment Injecting salt into PyCrypto KDF - useful?
Regarding your edit: Understood. That last link does talk about concatenation, but it is talking in the context of an ordinary hash function (which does not intrinsically support a salt). That's different from PBKDF2. PBKDF2 is designed to support salts, so the answer for PBKDF2 is different than for a vanilla cryptographic hash. Oleksi's answer remains the correct one.
May
8
comment What does $(\mathbb{Z}_n^*)^2$ mean?
I've fixed this answer for you. The standard answer is that $\mathbb{Z}_n^*$ is the multiplicative group of integers modulo $n$. There really is no other common usage for this (certainly not in cryptography). Ricky Demer is 100% correct.
May
7
comment Injecting salt into PyCrypto KDF - useful?
Thanks, Brian. Yeah, that resource you linked to is talking about something different: it's recommendation for concatenating password + salt relates to use of a hash like MD5 or SHA1 (which don't have any built-in support for salts, so manual concatenation is necessary), but not to PBKDF2 (which does have built-in support for salts, so you don't need to do it yourself). Even the PBKDF2 code sample on that page doesn't concatenate the salt + password; it passes them separately to PBKDF2.
May
7
comment Injecting salt into PyCrypto KDF - useful?
"some sources indicate" - Do you have links or citations to those sources? What argument did they give to support their position?
May
7
comment RSA leak bits to factor N
The problem requires that there has to be a PPT algorithm to compute these leaked bits (presumably, given $N,p,q$ as inputs). Do you have a plan for how to do that?
May
7
comment How do you find a cheater in Shamir Secret Sharing?
This question is closely related to crypto.stackexchange.com/q/6599/351