Lecture 3,4: Universal Composability

Protocol Initialization for the Framework of Universal Composability

Relations among Statistical Security Notions or Why Exponential Adversaries are Unlimited

In the context of Universal Composability, we introduce the concept of universal environments and simulators. Then, Universal Composability is equivalent to Universal Composability wrt. universal environments and simulators. We prove the existence of universal environments and simulators and investigate their computational complexity. From this, we get a number of consequences: First, we see th...

Relations amount Statistical Security Notions - or - Why Exponential Adversaries are Unlimited

In the context of Universal Composability, we introduce the concept of universal environments and simulators. Then, Universal Composability is equivalent to Universal Composability wrt. universal environments and simulators. We prove the existence of universal environments and simulators and investigate their computational complexity. From this, we get a number of consequences: First, we see th...

A Paradox of Quantum Universal Composability

Security of cryptographic protocols under composition is a major concern in cryptography. For classical cryptography Canetti gave a definition of security implying universal composability [Can01]. A protocol proven secure in that sense may replace ideal functionalities in arbitrary applications preserving the overall security of the application. In this contribution we sketch the modifications ...

An optimistic fair exchange protocol and its security in the universal composability framework

Fair exchange protocols allow both or neither of two parties to obtain the other’s items, and this property is essential in e-commerce. In this paper, we construct an optimistic fair exchange protocol that is applicable to any digital signature by prescribing three forms of signatures, namely presignature, post-signature and notarised signature. We set an expiration date for presignature, and t...