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I like crypto. Need I say more?


Mar
7
revised Hill cipher cryptanalysis - known plaintext known key size
added 1207 characters in body
Mar
7
comment Hill cipher cryptanalysis - known plaintext known key size
Can you post the cipher texts? Also are you sure the math is done mod 26 (that was my assumption)?
Mar
7
answered Hill cipher cryptanalysis - known plaintext known key size
Mar
6
comment Authenticated encryption without padding
I'm curious as to why the length cannot be increased. I can see that being an interesting theoretical question, but in practice I just don't see this being a real constraint. Sure, it might require some extra work to change some things (a protocol, database, or something along those lines). So, if this is indeed a hard requirement, I'd be interested in hearing more about your application.
Mar
6
comment Authenticated encryption without padding
@CodesInChaos looks like a valid answer to me. Care to post it?
Mar
6
reviewed Approve suggested edit on why inverse in diffie-hellman protocol will not give same value?
Mar
5
answered How to decrypt 3DES in ECB mode (using a wordlist)?
Mar
5
comment Entropy of Androids motion-sensor data
Entropy according to whom? In other words, what is your attacker model? Does the attacker have software implanted on the phone? If so, the entropy will be very low. Is the attacker allowed to video record the user shaking their device and take it back to the lab to analyze it, modeling the motion sensor to try to figure out what measurements were generated? Possibly low entropy in this case too. Or is the attacker assumed to not have software on the phone and not be within distance to gather information about the shaking process?
Mar
4
comment Why don't we use H(m||k) as a MAC?
See: crypto.stackexchange.com/questions/2669/…
Mar
4
comment How to decrypt 3DES in ECB mode (using a wordlist)?
So the wordlist represents plaintexts, correct? Do you have the encryption key?
Mar
3
comment Functional Encryption (for Non Experts)
My guess would be speed. It looks like asymptotically their scheme is pretty good, but by looking at how they construct their system, they probably have large constant factors in there that would kill performance in the real world. Implementation is probably non-trivial too.
Feb
26
comment My SSH server public key is 2048 bits, but my account's private key is 4096. What is my effective security?
The question is specifically about authentication as the OP says "My worry is that someone could brute force the private key and login to the server." Also the 2048 bit and 4096 bit keys that the OP was asking about do not affect an adversary's "after-the-fact" ability to break past session data, that is determined, as you state, by the DH parameters.
Feb
24
comment $f : \mathbb{Z}_n \rightarrow \mathbb{Z}^\times_n$?
Sounds like we have an answer for both possible definitions of "invertible". 1) yes - with 2 examples; 2) no - by the pigeon hole principle.
Feb
24
comment $f : \mathbb{Z}_n \rightarrow \mathbb{Z}^\times_n$?
@HenrickHellström, but not every element of $\mathbb{Z}_n$ is in $\mathbb{Z}_n^\times$ (if the latter is meant to be the multiplicative group of integers modulo $n$). The former has order $n$ while the latter has order $\varphi(n)$.
Feb
20
comment FHE - Brakerski's “Scale Invariant” Scheme
@RohitKhera, you may find this paper interesting: eprint.iacr.org/2014/062.pdf Apparently the scale invariant idea has been applied to BGV and to an NTRU based scheme.
Feb
16
revised My SSH server public key is 2048 bits, but my account's private key is 4096. What is my effective security?
added 73 characters in body
Feb
15
answered My SSH server public key is 2048 bits, but my account's private key is 4096. What is my effective security?
Feb
14
awarded  Enlightened
Feb
14
awarded  Nice Answer
Feb
13
answered Can someone explain the ECB Penguin?