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Aug
27
comment RSA was rejected by which journal?
What research have you done? Where did you hear this? Are you thinking of Merkle's puzzles?
Aug
24
comment Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
How are you going to represent the set of $2^n$ unique 64-bit vectors? What does that set look like? The answer is going to depend upon these details. Depending upon what your set of $2^n$ 64-bit vectors looks like, the answer might be very different. Therefore, we can't answer the question until you edit your question to give us that sort of information; I'm voting to close as "too broad". You can fix the question by editing it. (Also, I suggest you edit it to tell us what you tried and what research you've done on your own. You did do significant research before asking, right?)
Aug
24
comment How does compression before encryption leak info about the input?
"I'm pretty sure adding an "evil" chunk to a JPEG image won't leak the "good" part." - I don't know how you could possibly know that. Anyway, I believe my answer answers that question that was asked.
Aug
19
comment Simple proof that shows AES is not a uniform permutation on any n-bit string?
@Gilles, assuming the author means that it is uniformly distributed on the set of all permutations (when the key is randomly chosen)... the other thread proves that AES does not have this property. Of course, Dimitry's answer is an excellent answer, too.
Aug
19
comment Simple proof that shows AES is not a uniform permutation on any n-bit string?
possible duplicate of Block cipher and parity of permutation
Aug
15
comment Are there any cryptographic flaws in my webhook signing process?
@JessieA.Morris, for what it's worth, there are multiple different ways one can do TLS with client certs; they don't all require having a single trusted CA. But I've said my piece.
Aug
15
comment Are there any cryptographic flaws in my webhook signing process?
@JessieA.Morris, you're still creating your own mini-protocol. My advice stands. P.S. I'm not certain you mean by "work". Your statement that client-side certs introduce more work doesn't sound right to me. If you mean development cost, I don't agree. If you mean computation time, then I suggest you benchmark it, but I bet you'll find that TLS client certs are no worse than anything else that involves a client-side signature. Either way, if TLS+client certs doesn't meet your needs, you should clarify the question by being more precise about requirements.
Aug
15
comment Are there any cryptographic flaws in my webhook signing process?
Is there a reason you aren't just using client certificates? They were designed for solving this problem. The TLS folks thought a lot about the security challenges, so you wouldn't have to.
Aug
2
comment run length testing
This question looks off-topic to me. The site is for questions about cryptography (see here); your question does not appear to fit the fall within the scope of the site.
Aug
2
comment Theoretical attack on RSA
What's your question, specifically? This is not the place for open-ended questions ("Please leave opinions on that") -- this is for specific, answerable questions. In any case, this is a duplicate of the other question that Ricky Demer identifies.
Jul
31
comment Noise bound in FHE over the integers
@JongHyunKim, please don't use comments to ask a new question. Comments should only be used to help the author of the answer improve their answer. (This is not a discussion forum; see the faq for more details on how to use this site.)
Jul
29
comment Is it secure to use Diffie-Hellman key agreement to generate a nonce?
@YoavR., it sounds like you are using terminology in a non-standard manner. I don't know what you mean by "this is Nonce - by design it uses counter". I don't understand why you think a MAC "doesn't fit"; your explanation didn't make any sense to me. Again, if you want to receive help, edit your question to specify the security goals you are trying to achieve, what your requirements are, what mechanisms you have considered, what ones you have rejected, and why. I have to say this sounds like an instance of an XY problem.
Jul
29
comment Is it secure to use Diffie-Hellman key agreement to generate a nonce?
@YoavR., no, that is not correct. The purpose of an IV is not to prevent replays. The purpose of an IV is to provide confidentiality (to ensure that if the sender encrypts the same message twice, this won't be apparent to an eavesdropper). If you want to prevent replays, you should use a different mechanism: e.g., sequence numbers and a MAC. Please edit your question to describe what you are trying to achieve, as it looks very much like you are making some (incorrect) assumptions about the best way to achieve it.
Jul
29
comment Is it secure to use Diffie-Hellman key agreement to generate a nonce?
There's no need/reason to use Diffie-Hellman to generate a nonce. Instead, have Alice generate one nonce $N_A$, and have Bob generate another nonce $N_B$, and use both nonces -- or use the hash $H(N_A || N_B)$ as your random value. Alternatively, if all you want is an IV for a symmetric-key cryptosystem, you don't need them to cooperate to form a nonce: just have the sender generate the IV randomly. Both endpoints are presumably trusted (since they both know the shared key) and had better have been authenticated, so there's no need to combine both of their contributions to form the IV.
Jul
28
comment Elliptic Curve Cryptography
What have you tried? Do you know the equation that defines the tangent line?
Jul
28
comment Known plaintext attack on ElGamal encryption
What are your thoughts? What have you tried? Sounds like an exercise. We're not here to do your exercise for you; this is not a site where you can paste your exercise and we'll solve it for you. Instead, we expect you to make a serious effort, to show us what you tried in the question, and to formulate a specific question about a specific aspect of the problem or your approach.
Jul
28
comment CSPRNG that cannot be used as random extractor
@owlstead, OK, I've edited the answer accordingly, and to try to make it match my understanding. Now the answer makes more sense to me. AES CTR_DRBG is different from AES CTR.
Jul
28
comment CSPRNG that cannot be used as random extractor
OK, so I think part of the problem here is that you don't yet have a clear definition of what you mean by CSPRNG: what it is intended to achieve, what its API is, what its security definition is. A PRG is one well-defined notion in cryptography (AES-CTR, RC4, etc. are examples of a PRG). A CSPRNG is another, different primitive (Yarrow, /dev/urandom, etc. are examples of this primitive; it typically must accept non-uniformly distributed inputs, provide robustness to state compromise extension attacks, etc.). See my comment underneath otus's answer for some elaboration.
Jul
28
comment CSPRNG that cannot be used as random extractor
Based upon the answers it has become clear that there is some confusion about what you mean by CSPRNG (e.g., the distinction between CSPRNG and PRG). I suggest you edit the question to give us your definition of what you mean by CSPRNG: do you mean something like Yarrow, /dev/urandom, etc? or something like AES-CTR, RC4, etc.?
Jul
28
comment Whitening and randomness extraction
What definition of whitening would you like us to use? I have not heard the term "whitening" used in this particular context, so you'll probably need to define your terms (or provide some more context and more information about why you're asking and how you will use the answer) before I could answer this.