Updatable Encryption is a variant of symmetric encryption that allows to rotate the encryption key in the outsourced storage setting while minimizing the bandwith used. Indeed, any third party can update ciphertexts to the new key using a token provided by the key holder. UE schemes aim at providing strong confidentiality guarantees against adversaries that can corrupt keys and tokens. 

In this talk, I will give an overview of Updatable Encryption, show how to build post-quantum Updatable Encryption schemes using cryptographic group actions and give an instantiation based on isogenies. This is the first post-quantum Updatable Encryption construction not based on lattices and that allows an unlimited number of updates.

This is joint-work with Antonin Leroux (DGA-MI & IRMAR).

Reference: A. Leroux and M. Roméas. Updatable Encryption from Group Actions. PQCrypto 2024.