Questions tagged [universal-composability]

The framework of universal composability (UC) is a general-purpose model for the analysis of cryptographic protocols.

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Can ideal functionalities share variables

I am trying to define an ideal world for a protocol that requires two functionalities to interact with each other. Lets call them $\mathcal{F}_1$ and $\mathcal{F}_2$. Now $\mathcal{F}_1$ maintains a ...
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Are zkSTARKs simulation sound extractable in the random oracle model?

I've recently become interested in simulation sound extractable zero-knowledge proofs for use in UC-secure protocols. I've also become interested in the recent instantiation of PCIPs called zkSTARKs. ...
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Detail about reactive simulatability framework

I'm trying to understand the framework of reactive simulatability using *"PfWa2_00AsyncModel"* from this publication which is a tech report behind the paper A model for Asynchronous Reactive Systems ...
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Abstract Cryptography: why local simulators?

In the paper that introduced Abstract Crypto [MauRen11], the Theorem 2 page 15 states that, basically, if there exists some local simulators that can be pluged on a resource $S$ such that this new ...
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Why is this functionality chosen for UC-NIZK?

A correct proof (a proof which is indistinguishable from previously sent proof) can be tagged as wrong by the ideal functionality here if the adversary sends no witness. And, let's say P is a party ...
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Efficient universally composable protocols for aggregate statistics

Let's say we have multiple parties $P_1, \dots P_n$ that gather personal data, and a party $C$ that is interested in aggregate statistics on these data, i.e. the average value. An ideal functionality ...
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45 views

Proofs of security for anonymity in a multi-party setting

I'm looking for material that proves the anonymity of parties in a non-interactive setting. I would like to know if there are simulation based proofs (UC) and property based proofs (game based) for ...
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Are theorems 2 and 3 in the Town Crier paper (Zhang et al, 2016) proven using the UC framework?

I am reading the paper ‘Town Crier: An Authenticated Data Feed for Smart Contracts’ by Zhang et al (2016), but there is something I just cannot wrap my head around. In Section 7 and Appendix C, it ...
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What is the relation between an ideal protocol or functionality and an adversary model?

In the context of the UC framework, what is the relation between an ideal protocol or functionality and an adversary model? Does it make sense to specify the type of adversary an ideal protocol or ...
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Stand-alone vs UC and Non-reactive vs Reactive Functionalities

I'm looking for a simple and concise explanation for the following: What are crucial differences and similarities between UC and stand-alone security? Under what conditions does one imply the other?...
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Some questions about simulator in UC proof

Let's focus on the UC proof in the existence of the dummy adversary $\mathcal{D}$ and the simulator $\mathcal{S}$ that internally runs $\mathcal{D}$. My questions are: Is it true that $\mathcal{S}$ ...
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Question about PKI-based non-deniable authentication by Canetti et al

In Universally Composable Authentication and Key-Exchange with Global PKI, Canetti et al. proposed a non-deniable authentication functionality as well as a protocol that GUC-emulates it. My question ...