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I like crypto. Need I say more?


Oct
21
comment Security of cloud computational protocols in UC Framework?
@curious The PHD thesis I link to in the answer has an example. Also, chapter 4 of Ivan Damgard's MPC book has some examples. I do see your point. Typically it will depend on whether or not the cipher is computationally secure or information-theoretically secure. But you are right, for a specific cipher you will take the proven properties and reductions (e.g., ind-cpa assuming quadratic residuosity is hard) to argue the indistinguishability.
Oct
20
answered Encoding information in packet lengths to actively sidestep encryption
Oct
17
comment Simple digital signature example with number
If you let $\phi(n)=(p-1)(q-1)$ then we need an $e$ such that $gcd(\phi(n), e)=1$. In this case I just checked 5 and the gcd was 1, so I used it. You could pick $d$ instead and compute $e$ from it, but it is easy to mess things up and make RSA insecure if you do this and aren't careful.
Oct
17
comment Simple digital signature example with number
@KirillKulakov See en.wikipedia.org/wiki/RSA_(algorithm)
Oct
17
answered Simple digital signature example with number
Oct
16
revised garbled circuit vs fully homomorphic encryption
edited tags
Oct
16
comment garbled circuit vs fully homomorphic encryption
The output of a GC does not have to be in plaintext. If you don't want the person computing the function to know the output just have the output gates map to random values that only you know how to map those to the plaintext.
Oct
11
comment Is SHA-256 a one way permutation when restricting the domain to {0,1}^256?
See: crypto.stackexchange.com/questions/301/… I think it answers your question
Oct
9
comment How to prove the security of the PRNG?
+1, but how about PRNGs such as BBS which are at least reduced to well studied problems?
Oct
9
comment how much trust can we place in protocol verifiers?
Do you think that there is an objective answer to this question or will the answer be necessarily opinion based?
Oct
9
comment Are NIST's changes to Keccak/SHA-3 problematic?
In case anyone is interested the Keccak team responded to the article in question. Also, the Keccak team has written a response to the proposed changes.
Oct
9
comment post-quantum threshold secret sharing
What research have you already done? I personally am not a fan of existance questions though I don't think the site as completely resolved the issue. That said we do expect you to do some of your own research, etc. Tell us what you have found so far and why it doesn't meet your needs, etc.
Oct
7
reviewed Leave Open How hard/easy will be to break a SHA-1 or SHA-256 hash if the attacker knows part of the original text?
Oct
7
reviewed Leave Open Why are huge prime numbers important in cryptography?
Oct
7
reviewed Reviewed Does ElGamal Encryption create a different key for each block sent?
Oct
7
reviewed Reviewed SHA-1 colission resistance proof
Oct
7
reviewed Reviewed How hard/easy will be to break a SHA-1 or SHA-256 hash if the attacker knows part of the original text?
Oct
6
comment Does BouncyCastle (for ECC) resist timing attacks?
Depends on how you use them. You'll have to describe the app and how the crypto is to be used.
Oct
4
comment My encryption message system & question about security
Authenticating the server won't fix the problem if the key exchange is still in the clear. You'd need a strong key exchange (diffie-hellman, SRP, etc), even then there will be a number of issues. Browser based crypto is hardly ever a good idea. Perhaps instead of describing your solution to a problem you should describe the problem in detail (leave out the solution) and there are probably some very standard crypto protocols that will solve your problem.
Oct
4
comment Please punch holes in this authentication scheme
Impressive! I didn't see the second attack you outlined when I looked through it. Probably an important lesson there :)