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8h
comment How to use the non adjacent form (NAF) algorithm to implement scalar multiplication?
Bouncy Castle has a large number of elliptic curve operations available. Happy programming!
8h
comment What is the security strength of an n-bit HMAC?
"The effective security strength of the HMAC key is the minimum of the security strength of K and the value of 2C." So it isn't. For HMAC, the key size and key strength are usually 1:1 as 2C will be such a large value that it doesn't play any role. In other words, HMAC strength = key strength = key size.
12h
comment Security timestamp
what part of the wikipedia page and RFC 3161 don't you understand?
12h
comment Is it possible to enumerate the possible RSA keys?
The easiest trick for creating a small private key is simply to regenerate it with a well seeded PRNG. That way you don't need to compress the key itself. For the public key you'd probably require to compress the modulus. That's not easily done. You might however get away with creating a unique identifier over the modulus (i.e. hashing the value). If you then trust that unique identifier you can ask another party for the modulus when required.
1d
comment Which AES encryption do banks use?
This question is not very well stated. Your question in the title is way too broad; you don't even specify the interface you're talking about. Later it becomes clear that you mean browser connections to a specific bank. These cipher lists change all the time, and there are plenty of sites that will test which cipher suite is used. So this question is not a good fit for this site (or any other Q/A site - try a forum or online TLS test site instead).
1d
comment How to prove the security of block ciphers
I think the answer should probably be: 1. No, they are not proven beyond doubt, 2. security is measured by comparing them to other ciphers and trying known attacks and 3. yes. Note that we're not 100% certain that asymmetric crypto algorithms are necessarily secure. They are normally proven secure under some assumptions (e.g. that RSA cannot be factored fast on regular computers). For RSA and most other primitives, we're not certain about the hardness of the underlying problem.
2d
comment Examples of modern, widely used ciphers that suddenly fell?
Should we indicate in the question that we are talking modern ciphers that operate on bits rather than text? That way we can exclude the ciphers before the computer age for this already broad question.
Apr
29
comment Elgamal with secret key equal to zero possible?
You could wonder if it wouldn't be better to generate an all zero value and detect that there is a problem instead of generating a 1 and all zero's, which is equally insecure and doesn't show this issue. Having the implementation test for 0 and 1 and then break off with a strong warning that the PRNG is broken seems to be the best option. If the RNG was already tested you could just let it be.
Apr
29
comment How secure is the OTR protocol?
@otus Hmm, we already have a "yes, if the implementation is secure" answer, without much further depth. I'm still not sure if this question isn't too broad. I'll leave it be, but people may want to consider the value of the answers provide below.
Apr
29
comment Unknown Hash or Cipher
If it was generated by a keyed hash (e.g. HMAC) you would never find out. Your only hint would be the size of the encoded binary value. This puzzle is likely only going to frustrate you; I'd suggest you stop.
Apr
29
comment Currently Best Integer not bit FHE
You're not indicating what exactly is the problem with HELib, "unclear what you're asking" is one of the reasons to vote off topic. You're asking for FHE's that evaluate on encrypted integers, which is asking for references, which is off topic as well. Which one is best is asking for opinions, again: off topic. Please ask specific questions, do not assume we will do research for you.
Apr
28
comment Symmetric cipher speed (AES vs Camellia vs Twofish)
The final speed of ciphers depend on their implementation. If you want to perform a good comparison instead of hand-waving, you should compare the algorithms on a reference system using the algorithm implementations of your choice. If you're really serious about speed, you're more likely to find AES hardware implementations (e.g. AES-NI or ARM instructions) than Twofish implementations.
Apr
28
comment Currently Best Integer not bit FHE
What do you mean with "evaluates"? HELib readme shows that addition is supported; I suppose that they don't mean bit addition there, as bit addition is somewhat boring.
Apr
28
comment Best known attack
According to my answer that would be the one that compromises the security the most. What kind of information are you missing? What kind of conditions do you set? Please be as specific as possible.
Apr
28
comment Is there a standard for OpenSSL-interoperable AES encryption?
Ah, so openssl pkcs7 doesn't exist? Note the final question: "Is there a standard for OpenSSL-interoperable AES encryption?"
Apr
27
comment How robust is my coded output?
@Biv Yeah, your answer there practically takes care of the information of the comments here and the second part of my answer. They are nicely in sync :)
Apr
27
comment How robust is my coded output?
ECRYPT (EU) uses to run stream cipher competitions. I'm not sure if anybody is really interested in non-authenticated block ciphers - we've quite a few good ones. I could imagine tweakable block ciphers become subject to one. If that happens, look here (competitions at Dan Bernsteins cr.yp.to site)
Apr
27
comment How robust is my coded output?
Your current question isn't off topic Clarence - I would not have answered it if that was the case. But we get quite a few questions that simply show some ciphertext or a newly thought out algorithm and we have to close those. This was just a small reminder not to post such questions to you and other aspirant cryptographers.
Apr
27
comment How robust is my coded output?
Note that requests for analyzing a cipher are off topic here. You can however ask if specific parts of your design are considered secure with regards to current practices or not. Overly broad questions or questions that require original research shouldn't be asked here.
Apr
27
comment Backdoor in NIST elliptic curves
@SEJPM Smells like an answer to me, if you combine the two comments.