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comment Elgamal with secret key equal to zero possible?
You could use your argumentation for any fixed value $x$, say $x=288878347584375$. If the public key has this value $y=g^x$, then you know the secret key $x$. The point is that the keyspace is so large that this does not matter (because fixing any value will be hit with negligible probability). Consequently, you can safely ignore this problem and define $x$ to be the entire $\mathbb{Z}_q$. Clearly, this assumes that you are able to sample uniformly at random, i.e., have good randomness available at key generation - but in theory you assume this to be true.
Apr
26
comment Give a simple hash chain example in Java
I'm voting to close this question as off-topic because its a programming question and no crypto question.
Apr
26
reviewed Approve prg tag wiki excerpt
Apr
26
reviewed Approve prg tag wiki
Apr
26
reviewed Approve sha-1 tag wiki excerpt
Apr
26
reviewed Approve xsalsa20 tag wiki
Apr
26
reviewed Approve sha-1 tag wiki
Apr
26
reviewed Approve In RSA. Why is $\phi(n)$ kept secret and $n$ is public?
Apr
22
comment Why Victor must not know which tunnel Peggy chooses?
@aguellier The point is that simulatability gives you means to prove the zero knowledge property. Proofs of knowledge are a bit more involved and strengthen the soundness, but are very helpful in many cryptographic construction. If anything is not clear feel free to ask a new question and I will try to answer it.
Apr
22
reviewed Approve what is the difference between proofs and arguments of knowledge?
Apr
22
answered what is the difference between proofs and arguments of knowledge?
Apr
10
revised Shamir's Secret Sharing vs. Asmuth-Bloom scheme
Bug fix
Apr
1
reviewed Approve Why are there $q^2$ keys for each equivalence class in Pedersen-van Heyst Signature Scheme?
Apr
1
comment Why are there $q^2$ keys for each equivalence class in Pedersen-van Heyst Signature Scheme?
Please add the key generation of the scheme to make the question self-contained.
Mar
31
answered In case M is small is it possible to recover the message
Mar
26
awarded  Pundit
Mar
24
comment What is the difference between discrete logarithm and logarithm?
Reading is often a good starting point...en.m.wikipedia.org/wiki/Discrete_logarithm ...this does not help?
Mar
19
comment Selective and existential unforgability of signature schemes
Ah ok. Yes, that's perfectly possible. You can show how you can modify any SUF-CMA secure scheme such that it remains SUF secure, but is trivially EUF insecure. You can think about that ;) I guess I have time tomorrow to edit my answer.
Mar
19
revised Selective and existential unforgability of signature schemes
bug fixes
Mar
19
answered Anonymity problem after voting with blind signatures