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2d
comment does re-encrypting the same value with multiple keys reduce security
@ZackNewsham: as far as we know, multiple encryptions to different keys is not harmful in CBC-mode, even if the plaintext consisted of a single block, and even if the IV was constant between all encryptions (there are other reasons to randomize IVs; it just happens to be OK in this scenario).
2d
answered does re-encrypting the same value with multiple keys reduce security
2d
answered How to make sure the pre-agreed information safe for DH-Key Exchange
Apr
12
comment Why are collision attacks important when talking about MAC schemes?
I would like to point out that this arguments doesn't work when you start talking about MACs with nonces; in that case, if you model the nonce as a part of the state, then the probability of an internal collision between two different messages may be 0, because the two messages will always have different nonces.
Apr
11
reviewed Approve suggested edit on Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
Apr
11
answered How to keep phi(n) secret in RSA?
Apr
11
comment How to keep phi(n) secret in RSA?
We don't tell people what it is? The problem of finding $\phi(n)$ given $n$ is a hard problem (if $n$ is hard to factor). So, if we give people a number that they can't factor, and we don't give them $\phi(n)$, they can't determine it on their own.
Apr
11
comment Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
@tylo: try $x = p^2 - bp + b$. With that $x$, we have $x^x \equiv b \pmod{p}$ as an identity (assuming, of course, that $p$ is prime). Why is this? Hint $y^z \equiv (y \bmod p)^{z \bmod p-1} \pmod{p}$ if $p$ is prime.
Apr
11
comment Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
@SDL: for prime $p$, it is easy, unless you add in the restriction that $0 < x < p$ as K.G. said.
Apr
10
comment Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
Actually, if $p$ is prime, the problem of finding an $x$ such that $x^x \equiv b \pmod{p}$ is easy.
Apr
9
answered AES-256 Shift-Rows Offsets
Apr
9
revised What is h in the improved solution of RSA algorithm?
added 106 characters in body
Apr
9
revised What is h in the improved solution of RSA algorithm?
Added mention to a reference they apparently didn't read
Apr
9
answered What is h in the improved solution of RSA algorithm?
Apr
9
answered Secret Sharing 1 Required
Apr
9
comment Secret Sharing 1 Required
Is this homework?
Apr
8
comment What's wrong with this “order-preserving MAC” function?
You asked about a order preserving Message Authentication Code, MACs are assumed to be secure even in chosen text environments; a secret step size would easily be reconstructed if the attacker got one or two valid text/MAC pairs. And, even if the attacker didn't have any valid text/MAC pairs, we can estimate the size of a secret stepsize, by examining the MACs he does have; if they are all restricted to a small region, stepsize is likely tiny; if they span almost the entire range, stepsize must be large.
Apr
8
answered What's wrong with this “order-preserving MAC” function?
Apr
8
comment What's wrong with this “order-preserving MAC” function?
From what I see from the pseudocode, it would appear that $OPF(n)/stepsize - n \in \{0,1\}$. If so, it would appear that the function fails in its goal of "the adversary must not be able to guess the location of the points".
Apr
8
revised What benefit is there to using AES over my custom cipher for secure storage?
edited tags