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Feb
7
comment Does key renewal increase complexity of MAC forgery?
Thanks for the answer! So assuming the MAC is not broken, are (1) and (2) the only possible best attacks, depending on whether or not the tag is shorter than the key?
Jan
11
comment Is finding collisions in a part-hash not often enough a bad problem?
It's not possible to get collisions "less often than expected" because I'm pretty sure this bound is the tightest possible over all probability distributions (being lowest for a uniform distribution). Either you are miscalculating the bound, or generating your values wrong, your results cannot be correct.
Dec
10
comment Can homomorphic decryption of DES be practical?
@MaartenBodewes The algorithm doesn't need to be encrypted, but it does need to be realized as a homomorphic circuit...
Nov
14
comment Does complicating a flawed algorithm make it secure?
The answer is trivially "yes" since every secure encryption algorithm can be viewed as "added complexity" on top of the flawed identity cipher (which encrypts all plaintext to itself). But that is probably not the answer you wanted.. you need to be an expert to work out how to complicate it in a way that adds security.
Nov
9
comment What is the difference between “securely realizes” and “securely implements”?
You can also say "X is realized by Y" if that is less awkward to you. Ultimately it just means "to make real, concrete".
Oct
30
comment How is bitslicing faster?
@IlmariKaronen Fair enough, after reading your comments and the new answers I now agree it's sufficiently on-topic
Oct
29
comment How is bitslicing faster?
Is this really on-topic on Crypto SE?
Oct
25
comment I read ECB is bad because the same plaintext outputs the same ciphertext. Isn't that a requirement of a cipher?
I think a good addition to this answer would be to add a paragraph about how it's possible for a cipher to encrypt non-deterministically. The word "initialization vector" is referred to once and never explained.
Oct
21
comment Is there an existing cryptography algorithm / method that both encrypts AND compresses text?
The statement is correct, just somewhat awkwardly phrased. It is obvious that you cannot compress every single $n$-bit string into less than $n$ bits. You can compress some of them by exploiting redundancy (like repeated patterns of bits and so on), but others with less structure have to become larger after compression, at least by a single bit, to compensate, because information theory. So on average (and hence to guarantee correctness in all cases) the output must be as large as the input, or you will eventually truncate some input that didn't compress well (like, say, random bits).
Oct
9
comment Is there a cryptographic protocol that let's me prove someone has a large binary?
I don't have a full answer but I feel like a Merkle tree could probably tackle this kind of problem, maybe as part of some randomized protocol. Maybe someone else is more familiar with this.
Oct
7
comment Is it safe to initialize secret keys by just reading /dev/random on Linux?
@UnixJunkie The zero byte is a value just like any other, don't count on being able to store uniformly random data in null-terminated strings ;)
Oct
6
comment Generating unbiased numbers with a biased six sided die?
If Alice doesn't know the odds then she could also adapt the good old low-tech (but extremely clever) "unfair coin" technique, which might not be optimal but is easy to understand and thus probably more useful in real life with actual dice when two parties are trying to reliably use a biased die to carry out some kind of business. The unfair coin technique: roll twice, then HH -> rethrow, TT -> rethrow, HT -> output 0, TH -> output 1. I'm sure a variant could be devised for six-sided dice.
Oct
3
comment Can machine learning analyze random number generator?
This (probably) won't work. There is certainly structure in CSPRNG's that could potentially be exploited, but I don't believe naive classification will be powerful enough to yield a distinguisher for any nontrivial CSPRNG.
Sep
27
comment RSA: special parameters construction
Isn't $q$ going to be super small (assuming $e$ is small), given the density of the primes?
Sep
20
comment Maximum steganographic embedding rate not detectable by steganalysis?
Are you interested in scenarios when the detector may alter, corrupt, or delete part of the carrier (requiring redundancy and error correction, thus reducing embedding rate) or just the simplest case with a passive detector?
Aug
24
comment Encryption of 8 bit of block data
Does it have to be a block cipher?
Aug
19
comment File encryption with AES CTR mode
Citation needed... if you are reusing nonces in CTR mode you're not doing it right (and ditto if you're using CTR to encrypt hard drives)
Aug
3
comment RSA problem - how to find $d$
There are an incalculable number of threads on this site alone, let alone the whole internet, that address the process of deriving $d$ from $e$. Have you tried searching for them? Hint, there are at least two in the related questions list on the right.
Aug
2
comment Transforming Gaussian random $[0,1] $ numbers to uniform $[0,255] $
@dylan7 A byte is just 8 bits. To get a uniformly distributed byte, take 8 uniformly distributed independent bits and put them together (as in, binary notation).
Jul
31
comment How AES treat string input to encrypt data and what will happen if the cipher key is less than that expected?
If your key has less bytes than expected then it's not really a key, just something that you're trying to pretend is a key.