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seen Oct 24 at 14:30

Mar
19
comment How to verify a number encrypted with an unknown key
Do you have a source for the nth root ZKP?
Mar
5
comment Zero-Knowledge Challenge-Responce Protocol
I'm sorry but I still don't get why you need this ZK protocol or what it exactly is supposed to do. If an authority signs the one-way-key the voter gets the signature as well as the certificate of the signing key for verification. The voter now sends the polling station his vote, his signed public one-way-key and the certificate. Based on a PKI the polling station is now able to verify the authority's signature. There is no need to contact the authority.
Mar
4
comment Zero-Knowledge Challenge-Responce Protocol
I did not have a look at the paper you mentioned but in e-voting a voter usually gets something like an authentication token or a one-way signing key signed by an authority. For privacy reasons these signatures are often blinded.
Mar
4
comment Questions about proof of correct encryption in the Paillier cryptosystem
Assuming "revealing r" would provide any information about the summands of a Paillier homomorphically added sum. Would it help to use primes as random factors for the encryption of the summands? I mean an attacker then would have to find an efficient way to factorize the resulting r.
Mar
4
comment Questions about proof of correct encryption in the Paillier cryptosystem
Now that you mention it I come to realize that the proof can be passed on without loss of authenticity. Its obvious but I did not think of it. As for me this is only partially a problem. Is there a way to turn "revealing r" into an interactive version involving a challenge? Would this solve the problem of transferable proof?
Feb
27
comment Questions about proof of correct encryption in the Paillier cryptosystem
I understand why revealing r is a correct proof of encryption. Also the ZKP presented in the linked paper seems to be no voodoo. What I don't get is why the authors of the said paper claim that revealing r also reveals useful information. I was afraid I missed anything and decided to ask here before asking the authors.
Jan
29
comment In the Paillier cryptosystem, is there a method to judge whether an encrypted number is less than 0 (without the private key)
As far as I can judge this ponchos counter-example makes different assumptions. In his case the blackbox is available to anyone and does not require the cooperation of any other party. So an attacker can query the box with any input he likes. However, in case of the Zero Knowledge Proof (ZKP) the proof stringently requires cooperation of the secret-holder. The basic idea of any ZKP is that a prover applying a ZKP can never reveal more to a verifier than what he has already stated.
Jan
9
comment Why is RSA usually limited to messages up to 1 block
As far as I know the gain of a cipher from plain text to cipher text is called stretch factor. For a probabilistic cipher this factor is compulsorily larger than 1, i.e. the cipher text of a probabilistic cipher will always be larger than the corresponding plain text. So a +10% size for a probabilistic cipher does not sound that much for me.
Jan
9
comment Why is RSA usually limited to messages up to 1 block
I understand the general problem of message overhead.
Aug
9
comment Approach towards anonymous e-voting
@mikeazo: you are right, considering these keywords it should have been easy to find. However I feel there are billions of papers covering e-voting systems and might have lost myself a little bit in the mass. Thanks anyway for pointing me at this paper - the presented (N)IZK proofs look quite promising.
Aug
9
comment Approach towards anonymous e-voting
I thought about blind signatures, too. Blind Signatures guarantee anonymity and authenticity of the ballot. What they do not guarantee is correctness. So to guarantee correctness you need to check the ballots in advance or afterwards. Afterwards becomes problematic if ballots are to be added homomorphically. Checking in advance would require an extra trusted third party, something I'm desperately trying to avoid.
Aug
9
comment Approach towards anonymous e-voting
Also the system I'm planning is not 100% a real e-voting system and that is why not all requirements for such a system need to be satisfied. In fact some features of an e-voting systems are not desired at all.
Aug
9
comment Approach towards anonymous e-voting
I see D.W.'s point that re-inventing the wheel is rarely a good idea. However as mikeazo pointed out I'm trying to learn and experiment and this always includes making mistakes.
Aug
7
comment Approach towards anonymous e-voting
How would such a NIZK proof look like? I thought about this but everything I came up with either violated privacy/secrecy of a vote and/or did not rule out that the sum of the ballots might contain negative votes.