# Tag Info

4

What does this mean, exactly? The purpose of the environment is to model "everything else happening in the universe" besides the protocol execution. In the UC model, the adversary is allowed to talk to the environment during the execution of the protocol. So UC security means "security no matter what else is going on in the world, even if other things ...

4

Realizes vs Implements Given the context of the cited papers, they mean the same thing. That said, I would prefer realizes. Implements has a connotation of a source code implementation. There could be implementation flaws (buffer overflow, etc) that impact security. The protocol design is secure, but the implementation is not. That, to me, is the primary ...

3

This is very strange, and somewhat suspect. The abort here is one that prevents the client from getting output. However, the real-world adversary may behave in a way that the client does get output. I suggest writing to the authors to ask and/or going through this very carefully. Without having gone through the details at all, my initial guess is that this ...

3

Detection of malicious behavior can happen anywhere. However, it is not true that you can run semi-honest protocols and then check later. This is because such protocols can reveal the honest party's input when interacting with a malicious adversary. In such as case, even if you detect the cheating, security is not achieved. Thus, you need to make sure that ...

2

More generally, is it necessary to force the malicious party to act honestly is each intermediate step or it is sufficient to force him to output correctly? Detection of malicious behavior can occur at the end. It does not have to happen at each intermediate step. Is it possible for A to choose $x_i$s in a way that this protocol is also secure ...

1

EDIT: I realised that I assumed an IND-CPA game where the adversary has pre- and post-challenge access to the encryption oracle and not only pre-challenge access. I'll edit my answer soon. I'll give the idea and leave the concrete analysis to you. You want to show that single-query IND-CPA implies multi-query IND-CPA or in other words if there is an ...

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