Ciao a tutti, This Wednesday, 10 May, at 14:30 in D5.01 we are happy to welcome Giacomo Borin from the Università di Trento to the CQI seminar as a guest speaker. Giacomo will talk about his work on nonabelian-group cryptography, title and abstract below. As always you can join us online at https://meet.jit.si/cqi-demon-M6QW9V7YY. Looking forward to seeing you there, Will Speaker: Giacomo Borin Title: From Sigma-Protocols to Threshold Signatures and Secure Federated Learning Abstract: The first part of the talk will be about the design of signatures via the use of non-abelian cryptographic group actions, in particular the ones coming from coding theory assumptions. This family of schemes came to interest during the new NIST call for standardisation of signature designs, thanks to the trust of the community on their (quantum) resistance and the very malleable underlying structure. The core idea is to consider a zero knowledge proof for the knowledge of a secret group element $g$ such that $x’ = g \star x$ with $x,x’$ public, then render it to a signature (non-interactive protocol) via the classical Fiat-Shamir transform. Several schemes have been proposed with different instantiations of these assumptions: for example, LESS and MEDS use code equivalence (on different metrics). The mathematical structure of the group action can be exploited to optimize the schemes and to define a threshold version of the signature for any group action, moreover for the ones induced by linear code equivalence it is possible to exploit Abelian subgroups of the general linear group to achieve better parameters. The second part of the talk will be about the possible uses of the RLWE problem to achieve a secure post quantum federated learning (a machine learning technique that allows a set of users to train a shared model via local evaluated updated). To this end, we can use verifiable multi key homomorphic encryption to encrypt and aggregate the updates, that can then be validated via the use of zero knowledge proof for the range of the parameters.