International Association
for Cryptologic Research

A protocol has everlasting security if it is secure against

adversaries that are computationally unlimited after the protocol

execution. This models the fact that we cannot predict which

cryptographic schemes will be broken, say, several decades after the

protocol execution. In classical cryptography, everlasting security is

difficult to achieve: even using trusted setup like common reference

strings or signature cards, many tasks such as secure communication

and oblivious transfer cannot be achieved with everlasting security.

An analogous result in the quantum setting excludes protocols based on

common reference strings, but not protocols using a signature card. We

define a variant of the Universal Composability framework, everlasting

quantum-UC, and show that in this model, we can implement secure

communication and general two-party computation using a signature card

as trusted setup.