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They could use 1 out of 2 oblivious transfer. Alice offers the messages $0$ and $a$ and Bob uses $b$ as his choice bit (I.e., choosing the first message if $b = 0$ and the second if $b = 1$.). It should be easy to see that Bob now receives $a \land b$ (if in doubt write down the truth-table). Now Bob can send the result to Alice (or they can do the protocol ...


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Just to say you have tons of literature about that. If you need an entry point check out some papers here for instance: http://esorics2014.pwr.wroc.pl/page2/index.html#15 Read the introductions and the related work and follow the links to find the big seminal papers in the domain. Oh also, just a remark: it seems that you are looking for anonymity. if ...


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It can guarantee the integrity, because you can not fake another voting with the same hash. However, this only shows the ballot is casted correctly, but does not prove the ballot is correctly counted. And as you said, it can not provide anonymity, such as buying vote and coercion.


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Actually publishing your cipher will also be able to give you alot of feedback, FYI. An end-user opinions you will be able to collect without it, but your potential users' opinion sometimes looks priceless.


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Actually you're verifying the encoded part, and take a look at thoose "extra bytes". If they're an arbitrary/optional fields - it's ok to verify just an encoded part because the true purpose of verifying is check the encoding : they're complementary operations, and they alone are referenced to each other. The question you've risen is actually "Are the extra ...


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Not much in the cryptographic protocols themselves. But you can do other things to get around such attacks: Request signed read receipts, or received receipts. So, if I send a message from my phone to yours, it sends back a reply that your phone has received the message (or that you have opened it). If such a receipt is signed, your attacker might be able ...


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Message sequencing AND hash-tabling for a trail of backward messages. The loss of a single message is not a disaster, actually. To be not over-paranoid, implement "resend request" in your protocol. If it works and hashes are matched - it can be just a communication error. But if it fails - a line should be dropped immediately. Try to use Tor by the way, and ...


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I am having a hard time understanding your argument why you think this could be simulated. However, here is an explanation of why it could not. Assume Bob is honest and has input $y$, now we have to simulate the view of Alice. As the simulator, as you state, we only get the input and output of Alice. I.e, we only know $x$ and $f(x,y)$. We only need to ...


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Actually, it does not matter if Bobs number is greater or less than Alices number. In either case Bob can compute $n_A$ (here I denote by $n_A$ and $n_B$ the private numbers of Alice and Bob respectively). Bob could simply note the number of boxes with one pebbles in them and the number of boxes with two pebbles in them, lets call these numbers $p_1$ and ...


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The really important thing is, not encrypt-and-mac. The other two, you can debate, but both are at least theoretically sound -- one might just practically be better than the other. Encrypt-and-MAC falls apart for a very simple reason, though: the MAC is not meant to keep the plaintext secret. The MAC is based on the plaintext. Authentication is not designed ...


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It depends. If the entire input itself is within a DER encoded structure, then I would bug out. There is nothing defined for BER, CER or DER that would allow padding of structures within constructed values. If the input is just followed by additional data or junk bytes then it is up to the protocol or otherwise your discretion if you want to accept the ...


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I don't think there's an exact "correct" behaviour in this case. It would be up to the implementation to decide, since the spec is only concerned about the DER encoded portion. If your implementation parses the input as it moves along only, and doesn't concern itself with the overall size, then it would work fine. Having said that, I believe the best ...


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Assuming that your question excludes any kind of “regular” transmission error (which might also lead to one of the messages not reaching the receiver) the receiver should regard message #236 to be potentially malicious since the “ticket” (what you call “sequence number”) for message #236 can not be verified as genuine. The specific reaction to such a ...


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To prove that product holds over integers, one would start from commitments with groups of a hidden order. That is, proving party should not know order of the group, which is the case with RSA-like multiplicative group. Consider Prover responses $\rho_x = tx + \alpha_x$, $\rho_y = ty + \alpha_y$, $\rho_z = tz + \alpha_z$ to Verifier challenge $t$ with ...



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