Paper 2022/242

YOLO YOSO: Fast and Simple Encryption and Secret Sharing in the YOSO Model

Ignacio Cascudo, IMDEA Software
Bernardo David, IT University of Copenhagen
Lydia Garms, IMDEA Software
Anders Konring, IT University of Copenhagen

Achieving adaptive (or proactive) security in cryptographic protocols is notoriously difficult due to the adversary's power to dynamically corrupt parties as the execution progresses. Inspired by the work of Benhamouda et al. in TCC 2020, Gentry et al. in CRYPTO 2021 introduced the YOSO (You Only Speak Once) model for constructing adaptively (or proactively) secure protocols in massively distributed settings (e.g. blockchains). In this model, instead of having all parties execute an entire protocol, smaller anonymous committees are randomly chosen to execute each individual round of the protocol. After playing their role, parties encrypt protocol messages towards the the next anonymous committee and erase their internal state before publishing their ciphertexts. However, a big challenge remains in realizing YOSO protocols: efficiently encrypting messages towards anonymous parties selected at random without learning their identities, while proving the encrypted messages are valid w.r.t. the protocol. In particular, the protocols of Benhamouda et al. and of Gentry et al. require showing ciphertexts contain valid shares of secret states. We propose concretely efficient methods for encrypting a protocol's secret state towards a random anonymous committee. We start by proposing a very simple and efficient scheme for encrypting messages towards randomly and anonymously selected parties. We then show constructions of publicly verifiable secret (re-)sharing (PVSS) schemes with concretely efficient proofs of (re-)share validity that can be generically instantiated from encryption schemes with certain linear homomorphic properties. Finally, we show that our PVSS schemes can be efficiently realized from our encyption scheme.

Available format(s)
Cryptographic protocols
Publication info
A minor revision of an IACR publication in ASIACRYPT 2022
anonymity encryption publicly verifiable secret sharing YOSO
Contact author(s)
ignacio cascudo @ imdea org
bernardo @ bmdavid com
lydia garms @ imdea org
konr @ itu dk
2022-12-05: last of 2 revisions
2022-03-02: received
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Creative Commons Attribution


      author = {Ignacio Cascudo and Bernardo David and Lydia Garms and Anders Konring},
      title = {YOLO YOSO: Fast and Simple Encryption and Secret Sharing in the YOSO Model},
      howpublished = {Cryptology ePrint Archive, Paper 2022/242},
      year = {2022},
      note = {\url{}},
      url = {}
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