Fully Homomorphic Encryption (or FHE) is a set of cryptographic techniques that allows computations to be carried out directly over encrypted data, ensuring the confidentiality of data during calculations without prior decryption. However, so far, the security of FHE is not well understood beyond the basic CPA (Chosen Plaintext Attack) level. This talk aims to clarify the security of FHE in regimes beyond the CPA model. We focus on a specific security notion called CPA^D, in which the adversary Eve has more power than in the CPA model—specifically, she can also request the decryption of well-formed ciphertexts. Thus, in this work, we conduct attacks and propose new constructions in order to advance the understanding of FHE's security properties in the CPA^D security model.
Marina Checri is a young researcher who has just completed her PhD thesis at CEA List, Paris Saclay University, under the supervision of Renaud Sirdey and Jean-Paul Bultel. She is interested in Fully Homomorphic Encryption (FHE) and threshold multi-party protocols. Her work focuses mainly on security notions beyond CPA for FHE schemes.