Cryptology ePrint Archive: Report 2021/558

Verifiable Decryption in the Head

Kristian Gjøsteen and Thomas Haines and Johannes Müller and Peter Rønne and Tjerand Silde

Abstract: In this work we present a new approach to verifiable decryption which converts a 2-party passively secure distributed decryption protocol into a 1-party proof of correct decryption. To introduce our idea, we first present a toy example for an ElGamal distributed decryption protocol before applying our method to a lattice-based scheme. This leads to an efficient lattice-based verifiable decryption with only one server; it has lightweight computations as we reduce the need of zero-knowledge proofs. We believe the flexibility of the general technique is interesting and provides attractive trade-offs between complexity and security, in particular for the interactive variant where the online phase can be very efficient.

Category / Keywords: cryptographic protocols / verifiable decryption, MPC in the head, passively secure distributed decryption, lattice-based cryptography

Date: received 28 Apr 2021

Contact author: kristian gjosteen at ntnu no,thomas haines@ntnu no,johannes mueller@uni lu,peter roenne@uni lu,tjerand silde@ntnu no

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Version: 20210503:201150 (All versions of this report)

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