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1d
comment Types of Cryptography for a 4-8 bit microcontroller
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1d
comment What is the difference between IND-CCA2 and NM-CCA2? And how does one imply another?
What research have you done? Do you understand the difference between security notions? In its current state, the question lacks effort and information.
1d
comment Should I use a key store to keep my symmetric keys
Key management is a huge topic, and you can start at the usual references: wikipedia and google-searches. Then you can have a look what NIST has to say about key management.
1d
comment Elliptical curve cryptography key generation time
Concerning the naive approach: If you could do it that way, then brute forcing the key in the same manner would also be possible. Double-and-add is your only choice. (and its optimizations, especially NAF and wNAF are worth looking at)
Nov
25
comment When would one prefer a proof of knowledge instead of a zero-knowledge proof?
Proofs of knowledge are used for example to prove the knowledge of a trapdoor. If you consider discrete logarithms for an element $y$ to some base $x$, you want to prove that you know $\log_x y$. But obviously, you would also want your proof to be zero-knowledge in this case, or you could just state the solution and say "This is it, this is proof that I knew the solution".
Nov
24
comment Decrypt with only the cipher file and the key?
Concerning the keylength: Don't take the 13 symbols as set in stone.
Nov
24
comment Decrypt with only the cipher file and the key?
As a hint: If you look at the text in ASCII encoding, you can find repeating sequences. Compare the symbol-distance there with the key length... well, the usual classical-cipher things. If my guess is correct, it would be a cipher which was considered secure for about 300 years.
Nov
24
comment DHE key exchange. Is it really secure?
Humans are so bad at understanding exponential growth... Best example is the question "How often can you fold a paper, and guess how thick it will be" -> typical are 6 or 7, record is at 12 atm
Oct
22
comment How Secure is a Pronounceable Password? In means of entropy
What is enough entropy for your use? How long is that pronounceable password? Entropy for passwords from language are hard to measure, because you would have to know the likelihood of each syllable, etc. Then: Do you consider saying "hash", "dot" pronounceable? Most symbols have some form to speak them out.
Oct
20
comment Database row level encryption scheme
I don't think it is a scare tactic, it is a rule of thumb for people without the necessary background and experience. What you wrote is exactly what I meant: Memory management and the other aspects you mentioned are those pitfalls, which "amateurs" overlook and thus create software with massive holes in it. Simply coding the algorithm description of AES or RSA from a textbook is not enough. And usually, cryptographers also fall in this category: Quite often the people who design a new cryptographic primitive are not the ones implementing it.
Oct
17
comment Database row level encryption scheme
"It also runs faster in software which is what I will be implementing it in" => Are you a professional developer of encryption algorithms? If not, your security just lost all those nice theoretic properties: Don't implement cryptographic algorithms yourself, unless you're an expert. This is one of the hardest lessons to learn for software developers from other fields, but it is VERY crucial.
Oct
17
comment Is it true the longer the key length is the more secure the encryption?
Longer keys mean also longer minimum sizes of the actual data: You can't encrypt "half a block". E.g. if the blocksize is 1 MB, encrypted message with a single bit of information would be 1 MB. And it applies to both symmetric and asymmetric encryption schemes (and hash functions, and so on...)
Oct
15
comment Database row level encryption scheme
The FAQ states: "for software developers, mathematicians and others interested in cryptography". Cryptography is the science behind the application. It's like comparing architecture or structural analysis with masonry. And protocols are used by applications. They are not applications themselves.
Oct
14
comment Database row level encryption scheme
If you want actual security for a long period, get rid of that "14 character password" part. Unless you pick a uniform random key from the entire keyspace, this is not gonna be the highest security you can get. Other than that, none of those questions seem to be about cryptography but rather the application (which is off-topic most of the time).
Oct
13
comment Non-linearity of a boolean function
The term "Hamming distance" is actually not correct in this context, what you are looking for is the Hamming weight, and in this context it is very helpful to look at bent functions. They provide maximum non-linearity, but for actual cryptographic functions there are also other things to conside, e.g. bent functions can fail to have an output with roughly uniform distribution of 0 and 1. Anyway, that article should give some insights.
Oct
8
comment How do I generate a number for a lottery and later proves its existence
What do you mean by short collision? A partial collision? That's not gonna help in this case. If you can break collision resistance of HMAC, then this is broken, yes. This isnt perfectly binding, I know, but unless you can break collision resistance, hash functions (or something like HMAC) are computationally binding for everyone.
Oct
7
comment side channel attacks on AES
This section on Wiki describes all side-channel attacks I know of (mostly cache timing and fault injection). But all of them kinda require the ability to run a program on the same machine or otherwise have some control over the machine (e.g. for fault injection). But if this is relevant to you, depends on your application/server. Some speculation: There was some nifty side-channel attack based on an RSA implementation based on the noise of the processor. Maybe no one has looked into that for AES ;)
Oct
7
comment Can adding nonces make challenge response authentications weaker?
I think, adding more nonces does not change a thing. The most important aspect of a nonce in an authentication scheme is that it prevents the attacker from just replaying a recording of a previous authentication process. If your server actually makes sure that nonces are only ever used once, you gain nothing. If you just draw a random nonce, you reduce the chance of having the same nonce again... but at a bitlength of 80+ bits, this probability doesn't matter, kinda.
Oct
7
comment How do I generate a number for a lottery and later proves its existence
Uhm, how do you break the binding property of an actual hash function "fast", e.g. SHA256? I mean, for that you would have to break at least collision resistance.
Oct
7
comment Are hash functions chaotic?
There are no real numbers in digital algorithms. And floating point rounding error is nothing comparable to actually unstable systems in the mathematical sense.