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I like crypto. Need I say more?


Nov
12
comment How do I cryptanalyze a password field?
Continued: is there an obvious block length? In other words, do the sizes of all ciphertexts have some common multiple (like 40 bits or 80 bits). If you can access many, many ciphertexts, what is the entropy? If the entropy isn't high, it might be an encoding scheme instead of encryption.
Nov
12
comment How do I cryptanalyze a password field?
Since you know one plaintext/ciphertext pair, here are a few questions that if I were trying to figure it out I would want to know. Is the ciphertext deterministic for a single user? Is it deterministic across multiple users? You say the lengths are not the same. Do same length passwords have same length corresponding "ciphertexts"?
Nov
12
comment How do I cryptanalyze a password field?
The question was not closed because of my suggestion. It was closed because requests to analyze or decrypt data are off topic. See the FAQ. The stackoverflow folks warned you this might happen if you go back there and read the comments. I'd suggest you look at the FAQ for what is on topic and edit the question to make it on topic, then we might be able to help.
Nov
11
comment How do I cryptanalyze a password field?
From the information you have given, I think the best advice you can give your customer is to switch applications. It is highly likely given the details you've provided that the password storage is not very secure. Makes you wonder what other mistakes the developers made.
Nov
10
awarded  Nice Answer
Nov
5
comment Is multiplicative secret sharing secure?
I assumed that $\mathbb{Z}_n^*$ was, by definition, elements that are co-prime to $n$. Either way, I appreciate the answer.
Nov
5
comment Is multiplicative secret sharing secure?
I guess your caveat (assuming $p$ is prime) confused me. To have a multiplicative group $p$ doesn't have to be prime. Is the issue in the case of non-prime $p$ sampling uniformly?
Nov
5
comment secret sharing of product of 2 numbers
@freak_warrior, FYI I asked a specific question about the multiplicative version: crypto.stackexchange.com/questions/11535/…
Nov
5
comment Is multiplicative secret sharing secure?
Is it also (information theoretically) secure for the multiplicative group of the finite field $GF(2^n)$?
Nov
5
asked Is multiplicative secret sharing secure?
Nov
5
reviewed Approve suggested edit on Threshold cryptosystem with a required share
Nov
5
awarded  Nice Question
Nov
5
comment What is so special about elliptic curves?
The ECs that you see that look nice are over the reals. The elliptic curves over finite fields do not look that way at all. In fact they look pretty random which is another reason they are good for cryptography. AFAIK other functions over finite fields do not form a group.
Nov
5
answered What is so special about elliptic curves?
Nov
4
comment secret sharing of product of 2 numbers
@freak_warrior, no $a_j+b_j$ gives a share of $a+b$, $a_jb_j$ gives a share of $ab$ but with the caveats listed above.
Nov
2
comment RSA 896 vs 1024 vs 2048 in Javascript?
Why are you not using RSA for key exchange and then use symmetric encryption for confidentiality and integrity?
Nov
2
answered secret sharing of product of 2 numbers
Nov
2
comment secret sharing of product of 2 numbers
What secret sharing technique are you using? Shamir?
Nov
1
revised Question about the definition of a perfect cipher
deleted 7 characters in body
Nov
1
comment Question about the definition of a perfect cipher
@PaŭloEbermann correct and important since the keyspace is larger than the ciphertext space. I'll fix it.