International Association
for Cryptologic Research

Name: Phan Duong Hieu
Topic: Sécurité et efficacité de schémas cryptographiques
Category: public-key cryptography

Description: Provable security is nowadays one of the major lines of research in Cryptography. It aims at providing security proofs of cryptographic schemes in a complexity–theoretical sense: if one can break the scheme, one can solve the underlying problem. Provable security is strongly related to three main trends in the development of Cryptology: formalization of security notions, design of cryptographic systems, and development of new cryptographic features.\r\n
\r\nIn this thesis, we first deal with notions of security in both asymmetric and symmetric encryption. We study more in detail the relation between different attack models in asymmetric encryption. We also establish the relation between the notion of (super) pseudo–random permutation and that of semantic security in symmetric encryption.\r\n
\r\nSecondly, we propose new efficient constructions for asymmetric encryption in the random oracle model (new paddings for encryption, and universal paddings for both encryption and signature). Furthermore, we introduce a new class of public–key encryption schemes: chosen ciphertext secure schemes without redundancy. Up to now, redundancy used to be required for proofs of security in public–key encryption schemes.\r\n
\r\nFinally, we consider the traitor tracing problem in broadcast encryption and we introduce a new feature: public traceability. We construct a basic scheme with such feature, and then generalize it to achieve almost optimal transmission rates.[...]