## Witness-authenticated key exchange revisited: Improved models, simpler constructions, extensions to groups

[Matteo Campanelli](https://research.protocol.ai/authors/matteo-campanelli/), [Rosario Gennaro](https://research.protocol.ai/authors/rosario-gennaro/), Kelsey Melissaris, [Luca Nizzardo](https://research.protocol.ai/authors/luca-nizzardo/)

[Cryptonet](https://research.protocol.ai/groups/cryptonet/)

[Cryptography](https://research.protocol.ai/areas/cryptography/), [Distributed systems](https://research.protocol.ai/areas/distributed-systems/)

## Abstract

We revisit the notion of Witness Authenticated Key Exchange (WAKE) where a party can be authenticated through a generic witness to an NP statement. We point out shortcomings of previous definitions, protocols and security proofs in Ngo et al. (Financial Cryptography 2021) for the (unilaterally-authenticated) two-party case. In order to overcome these limitations, we introduce new models and protocols, including the first definition in literature of group witness-authenticated key exchange. We provide simple constructions based on (succinct) signatures of knowledge. Finally, we discuss their concrete performance for several practical applications in highly decentralized networks.

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