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Nov
11
comment Permutation parity after cycle-walking
The standard trick for small block Feistel ciphers is to use modular addition, rather than xor, in each round; that way, the round, and hence the permutation, has a 0.5 probability of being odd.
Nov
11
reviewed Leave Open what is SALSA20 Nonce and its requirements
Nov
11
revised Why is this cryptosystem insecure?
edited body
Nov
11
comment Why is this cryptosystem insecure?
Kairos, now that you got it, might I suggest you answer the question below? That way, other people looking at the question later will see the answer, not just the hints (and it will firm up in your mind exactly what the answer is)
Nov
11
comment Why is this cryptosystem insecure?
Hint: what is $g_1 \bmod p$? How can the attacker use that to factor $N$?
Nov
10
reviewed No Action Needed Are modified implementations of cryptographic algorithms a good idea?
Nov
10
comment How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?
Hint: suppose that you found a way to show that your new scheme is not CPA secure; can you use that to show that the original public key encryption scheme is also not CPA secure?
Nov
10
reviewed No Action Needed How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?
Nov
9
reviewed No Action Needed Do OpenPGP SmartCards have the same or better security than an air-gapped machine?
Nov
9
reviewed No Action Needed The number of surviving key after “Meet in the middle stage” in 3-subset MITM attack
Nov
9
reviewed No Action Needed Why is there an extra block when encrypting?
Nov
9
reviewed Close RSA: Fermat-Euler Theorem - coprimality of message and modulus
Nov
8
comment Signature scheme doesnt seem to hold
$g$ is of order $q$ if $g^q \equiv 1$ (and if there is no smaller $q > 0$ where this holds; although that's actually not important in this case). In your example, $g$ is of order 22. An alternative value with order 11 would be $g=2$
Nov
8
answered Signature scheme doesnt seem to hold
Nov
7
reviewed No Action Needed Can we give access to controlled functionality in Fully homomorphic encryption schemes?
Nov
7
reviewed No Action Needed recommendation to see documentaries about history of cryptography
Nov
7
comment Random Permutation polynomial
@user153465: There are $q!$ permutations on a set of $q$ elements; for each permutation, there is an unique order $q-1$ (or shorter) polynomial where the output of the polynimial is the input permutated by that permutation; QED
Nov
7
reviewed No Action Needed What is the value of Q such that Q|P-1 where P is a prime number?
Nov
7
comment Zero Knowledge Example using discrete log
You stated that 'you don't get any information about x, because ... the result y [is] random"; that is a claim about informational security -- I just mentioned that it is not accurate. And, in any case, this really isn't an answer to the question; see Thomas's response for the correct answer ("it isn't that $g^x \bmod p$ doesn't leak any data, but that a ZKP doesn't leak any additional information")
Nov
7
comment Crypto-Compression Algorithms?
"usually in cryptography it is unwittingly assumed that the input data to encryption block is already fully compressed" -- huh? In cryptography, we explicitly make no assumption what the plaintext looks like; we expect the encryption to be secure whether the plaintext is fully compressed, or is extremely redundant (e.g. consists of all zeros), or somewhere in the middle.