Marsh Ray

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	972 reputation	bio	website		visits	member for	1 year, 9 months
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Mar 29	comment	Can a user of a password-protected Wi-Fi sniff on other user's communication? When I've looked into wifi hacking, it sounds like a pretty common technique is to DoS the client over the air until it drops and reconnects. I believe this allows the attacker to observe the nonces exchanged at the initial handshake.
Mar 21	comment	Is the SILC protocol still used? Probably mpOTR would be a better choice for new usage.
Jan 7	comment	Implementation of Tao Xie and Denguo Feng's MD5 attack No, he asked about a specific attack. The link you posted is from 2005.
Dec 14	comment	What does SSL use? RSA? El-Gamal? Elliptic curves? DSA is based on El-Gamal, so you could use DSA certificates. But you're right, no one does.
Sep 11	comment	How do I construct a 256-bit hash function from 128-bit AES? I had to do this years back for something inconsequential. I'm sure that what I came up with is crappy. Thankfully, what I though was inconsequential back then remains inconsequential today, but that is notoriously hard to predict in advance. Other times that has not been the case.
Sep 11	comment	How do I construct a 256-bit hash function from 128-bit AES? You feel that 'Hirose - Some Plausible Constructions of Double-Block-Length Hash Functions' iacr.org/archive/fse2006/40470213/40470213.pdf is insufficiently vetted?
Sep 1	comment	How are constructs with data-dependent swaps and rotations cryptanalyzed? If only I could have accepted both answers. Instead, I flipped a fair coin.
Sep 1	comment	How can we reason about the cryptographic capabilities of code-breaking agencies like the NSA or GCHQ? I think it's an interesting question and one that every user of cryptography outside of the US Government itself must be asking. While it's true that an organization such as the NSA gives up very little information about its capabilities (and the question could be more general and apply to all such organizations) the amount of information is non-zero. Even in the absence of information, the question degenerates to another interesting and important question: why should we have confidence that algorithm X is secure in principle?
Aug 28	comment	If a cryptanalytic breakthrough is made, what process should be followed? First of all, you should never assume that you're the only party that knows about it.
Aug 28	comment	If a cryptanalytic breakthrough is made, what process should be followed? I think there's enough history and data at this point that we can say full disclosure is a good principle and default course of action. Generally the only parties opposed to it are those who actually want (perversely) the vulnerable state to persist longer.
Aug 26	comment	Does MD5 generate 128 independent bits? I'm far from an expert on this topic, but it seems to me that MD5 is completely deterministic, so when does it even make sense to ask about its stochastic properties? E.g., maybe in an attack context we could state something in terms of the absence of any (tractable) expression to constrain the input domain only slightly but that significantly modifies the distribution of some expression made from the output (or output and input) bits.
Aug 26	comment	Does MD5 generate 128 independent bits? Hmm, if the input is "random and at least of the output size" even the identity function achieves independence among the output bits. Is that a reasonable constraint for any useful interpretation of the question? The other extreme of two inputs seems like a better interpretation for crypto.se. An adversarial environment probably needs to be concerned with the worst case.
Aug 26	comment	If a cryptanalytic breakthrough is made, what process should be followed? @Paŭlo I agree that the field of cryptography needs to be able to discuss attacking and defending in a completely abstract way, using the terminology such that it's unloaded from the ethics of any particular human situation. More often than not, it's the real-world defender who benefits from the 'attack' research anyway. Nevertheless, it's probably not a good idea for any researcher to be completely oblivious to the real-world implications of their research. It think it's an important (even if maybe a little far-fetched) question that needs to be asked. If not here, then where?
Aug 24	comment	Is HTTPS secure if someone snoops the initial handshake? @David Let's not assume it isn't broken, or that there aren't some conditions in the fine print somewhere that have to be satisfied in order to actually realize the implied security.
Aug 24	comment	Looking for cryptographic secure hash algorithm(s) that produces identical root hash for differently sliced hash list Why do you want to know if two users upload the same file if you don't know the content of the file? You can't exactly give the ciphertext from one user back to another without also giving him the decryption key.
Aug 22	comment	Dictionary attack on pass-phrases on common algorithms Except that XKCD is showing a four word pass phrase at 44 bits of entropy by choosing 4 words from a 2^11 entry dictionary. He's not saying it's more secure because of the plain string length.
Aug 22	comment	Is digest=HASH(HASH(a)+HASH(b)) equivalent to publishing two digests? They're only 20 bit strings. You can sort those even in a language without loops.
Aug 22	comment	Dictionary attack on pass-phrases on common algorithms @gokoon English is, effectively, a small list of words.
Aug 19	comment	Now that quantum computers have been out for a while, has RSA been cracked? He must not be a very good salesman if he's only sold two customers. No wonder he's having problems.
Aug 18	comment	How long would the 100 Year Cryptography Project have secured its data had it been started 100 years ago? The point about things being qualitatively different back when crypto was all military secrets is well-taken. Nevertheless, world-class experts were certainly collaborating in teams within the scope of their own secrecy, which could still be quite impressive. (Bletchley Park cf. Eurocrypt 2011 anyone?) Collaboration in a restricted scope certainly has disadvantages, but being well-funded and focused has its own advantages too. Is it any more unfair of a question to them than to those attempting such a project today? Maybe, perhaps.