# All Questions

534 views

### Case insensitive verification of HMAC / Base64 signature

I am signing a short message using the base64 of an HMAC, like this (python): ...
161 views

### How fast can a wrong decryption key be detected using ECC?

When can a decryption function detect that the ECC key I use for decryption is incorrect? Is it possible to do that during initialization, or does the complete message have to be decrypted to do that?
120 views

### Why constrain the message lengths in indistinguishability in the presence of an eavesdropper?

I need your help with a very basic concept in cryptography which I can't understand/prove on my own. I'm trying to prove and understand why, under "indistinguishability in the presence of an ...
673 views

### How is ElGamal not secure under chosen ciphertext attack, but semantically secure in some cases?

I know that you can create a ciphertext c' using c and then find the corresponding m' for c' which you can use to find m for c. So, doesn't this mean that it is not semantically secure? But I also ...
241 views

### Chosen ciphertext insecurity in an ElGamal variant

I'm trying to prove something and if I can show that there is a simple way to calculate $(g^a \bmod p)^k$ if I know both $g^k \bmod p$ and $g^a \bmod p$, then (I think) it will help me prove it, but I'...
266 views

### Efficient decoding of irreducible binary Goppa codes and the role of matrix P in McEliece cryptosystem

If we assume that the support for an irreducible binary Goppa code $\gamma_1, ..., \gamma_n$ is publicly known, when is it possible to efficiently decode the code? I know it's possible if one knows ...
458 views

### DSA signatures with related k and unknown payloads

Suppose that we are given DSA parameters $p$, $q$, $g$, a public key $y = g^x$, and two signatures $(r_1,s_1)$ and $(r_2,s_2)$. We are told that $(r_1,s_1)$ and $(r_2,s_2)$ were produced by related ...
769 views

248 views

### State of the art in zero knowledge proof compilers?

What is the current state of the art zero knowledge proof compiler ? I need one that can minimally handle double exponentiation by a known value E.g. $$Pok\{(\alpha):h=g^{\alpha^b}\}$$ where b, ...
2k views

### What is the difference between a hash and a permutation?

As defined by Wikipedia a hash function is [...] any algorithm or subroutine that maps large data sets of variable length to smaller data sets of a fixed length. For example, a person's name, ...
Is there a practical homomorphic encryption scheme that can give reasonable execution time results in computing a dot product: $$a_1*b_1 + a_2*b_2 +a_3*b_3 +\ldots+ a_n*b_n$$ I imagine the scheme will ...