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seen May 9 at 0:59

Sep
22
comment Accelerating SHA-1
@jug: I've never heard this before (that Intel is quite a bit faster on a single core)... can you point me at a reference for this? I'd like to see if switching hardware would help.
Sep
21
comment Accelerating SHA-1
@jug: I did find that link, which is what led me to updating to the latest OpenSSL. Unfortunately, it was no faster.
Sep
21
comment Accelerating SHA-1
@Samuel: I'm processing a single incoming stream arriving at 5Gbps from the network and I'm currently bottlenecked by SHA-1 at 2.6Gbps; you're right that SIMD is useful: the XMM and YMM registers are part of the SSE(1-4) instructions which are already used in the OpenSSL code.
Sep
20
comment Accelerating SHA-1
Thomas: the authors of the paper I cite in my answer claim that a GPU does help. But they talk about "SSL flows" so perhaps they are inducing parallelism this way?!
Sep
20
comment Accelerating SHA-1
@fgrieu: I'm hashing 128KiB at a time via SHA_Update (OpenSSL) in a tight read loop. I need a hash for the entire file, so I cannot run hash invocations in parallel (since SHA1 needs the previous chaining value to start computing the next).
Sep
20
comment Accelerating SHA-1
I have some latitude with the protocol... you're thinking to hash separately on multiple cores?
Sep
19
comment Converting a stream cipher into a block cipher
I'm asking out of general interest; to me it's interesting if one primitive can be efficiently converted to the other.
Sep
4
comment Is modern encryption needlessly complicated?
Modern crypto is needlessly complicated; but not because of the (simple) primitives like RSA, DES, and AES. It's universality composability and ZKPs that are the problem.
Sep
2
comment What is the sign bit for in Feige-Fiat-Shamir?
In HAC, 10.26 step b (p. 410) the authors claim that the sign is required to avoid leaking information. I can only guess that this information is the fact that $I_j$ is a square, which seems to not really be very useful (after all, you can't take the square root!). A simulator could produce this same distribution, right? Just generate a random square.
Sep
2
comment What is the sign bit for in Feige-Fiat-Shamir?
Hm, I'd never heard of "unrestricted input" ZK before. But in the excerpt you quoted above, FFS say that we must have our $I_j$ range over all Jacobi symbol +1 values for ZKPs of knowledge. They don't mention "unrestricted input" (perhaps they have some definition of ZK that requires it I guess).
Sep
2
comment What is the sign bit for in Feige-Fiat-Shamir?
It's more than this. The FFS scheme equiprobably multiplies each $1/S_i^2$ by -1 or 1. Since -1 is a non-square with Jacobi symbol 1 (because $n$ is a Blum integer), this preserves the Jacobi symbol while expanding the range of values produced. I don't know why they do this (and the wikipedia version doesn't do it at all).
Sep
1
comment What is the sign bit for in Feige-Fiat-Shamir?
The section you cite seems to be a (slightly) different scheme from the one cited in wikipedia (the wikipedia entry doesn't even contain the $I_j$'s; I wonder if it's correct?!)
Sep
1
comment Should we MAC-then-encrypt or encrypt-then-MAC?
Also see the unpublished paper at citeseerx.ist.psu.edu/viewdoc/…
Aug
28
comment How does asymmetric encryption work?
Agreed regarding your specific constant, but perfect squares are easy to factor and there an infinite set of them. The fact that semiprime n=pq is vulnerable for certain values of p and q has led to the recommendation that p and q be "strong primes" in some RSA standards. (en.wikipedia.org/wiki/Strong_prime).
Aug
27
comment How does asymmetric encryption work?
Ah, like a semiprime then (en.wikipedia.org/wiki/Semiprime). These are not always hard to factor (perfect squares being the obvious example) but usually are, yes.
Aug
27
comment How does asymmetric encryption work?
2^{243112609} is a very large number near a prime (it's one more than a prime). And I can factor it in my head.
Aug
27
comment How does asymmetric encryption work?
I would be careful to avoid saying that factorization is "extremely hard" but instead say that "no one knows how to do it efficiently." (And the truly correct statement is that "no one in the public community knows how to do it efficiently.")
Aug
25
comment Can you create a strong blockcipher with small blocksize, given a strong blockcipher of conventional blocksize?
Thanks. Do you have any familiarity with the Morris, Rogaway, Stegers construction that uses Thorpe shuffles? (cs.ucdavis.edu/~rogaway/papers/thorp.pdf)
Aug
24
comment Can you create a strong blockcipher with small blocksize, given a strong blockcipher of conventional blocksize?
Thanks Jack. I had never heard of FPE, but it's exactly what I was looking for.