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Feb
20
revised What informal indicators exist for estimating the computational infeasibility of cryptographic problems?
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Feb
20
asked What informal indicators exist for estimating the computational infeasibility of cryptographic problems?
Feb
16
comment My SSH server public key is 2048 bits, but my account's private key is 4096. What is my effective security?
@Gilles: Right, the question makes more sense if the second key is a public key server side, and is used for client auth.
Feb
14
comment Why is a 2048-bit public RSA key represented by 540 hexadecimal characters in X.509 Certificates?
Minor nit: X.509 objects are always DER encoded and not just BER encoded. DER is a subset of BER, so you might decode any DER encoding with a BER decoder, but the converse is not (necessarily) true, because DER encoding is unequivocal, while BER encoding is not.
Feb
10
comment How can I simulate and measure brute force hacking using RSA?
160 bits sound about right if by "brute force" one means literally iterating through all odd numbers from $\sqrt(N)$ and checking if the value divides $N$.
Feb
8
awarded  Yearling
Feb
5
answered Do both client and server need to implement OpenSSL protections to protect from CBC attacks
Feb
4
awarded  Nice Question
Feb
3
comment Can passwords be stored securely so that a similarity comparison can be made?
No, it would just require storing $h = Hash(f(PW))$. If $PW_0$ and $PW_1$ are similar, then $h_0 = h_1$.
Feb
3
comment Can passwords be stored securely so that a similarity comparison can be made?
One answer would be that the entered passwords are always passed through a function $f$ such that $f(PW_0) = f(PW_1)$ iff the passwords are "similar". One trivial example would be converting all entered passwords to all lower case before further processing.
Feb
2
comment What is difference between PRG, PRF, and PRP
It would be a stretch, so not quite. A PRF has to be indistinguishable from a random function. A PRP might be, but doesn't have to be, a PRF in this sense. However, the security proof for e.g. CTR mode is based on the premise that the block cipher (a PRP) might be modeled as a PRF, as long as the key stream is constrained to the square root of the cardinality of the total set of possible blocks.
Feb
2
comment Proof for exponentiation in modular arithemtic
This is a proof by induction. We know it is true for $e = 1$. Using the formula in the answer, we can then prove it is true for $e = 2$ as well, and then for $e = 3$ etc. No matter how large $e$ gets, we might prove that the formula is true for $e + 1$ as well. Hence, by induction, it is true for all integer values of $e$.
Feb
2
comment What is difference between PRG, PRF, and PRP
The difference between a PRF and a PRP is that the PRP is a bijective function and the PRF is not. There are no other differences, but of course this difference has various implications for their respective applications.
Feb
2
answered Why is CBC based on AES malleable in blocks other than the first block?
Jan
30
revised Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
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Jan
30
revised Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
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Jan
30
revised Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
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Jan
29
revised Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
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Jan
29
revised Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$
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Jan
28
comment Secret sharing - no dealer, modifiable, verifiable
If robustness isn't a requirement, also look at Pedersen's original scheme link.springer.com/chapter/10.1007%2F3-540-46416-6_47