Relations between semantic security and anonymity in identity-based encryption

Javier Herranz (1) , Fabien Laguillaumie (2) , Carla Ràfols (1)

1 MAK - Departament of Matemàtica Aplicada IV Mathematics Applied to Cryptography
2 Equipe AMACC - Laboratoire GREYC - UMR6072

Semantic security and anonymity are the two main properties that an identity-based encryption scheme can satisfy. Such properties can be defined in either an adaptive or a selective scenario, which differ on the moment where the attacker chooses the identity/ies that are the target of the attack. There are well-known separations between selective and adaptive semantic security on the one hand, and between selective and adaptive anonymity on the other hand. In this paper we investigate the relations between these selective and adaptive notions, for identity-based encryption schemes enjoying at the same time some security and anonymity properties. On the negative side, we prove that there is a separation between selective and adaptive anonymity even for schemes which enjoy adaptive semantic security. On the positive side, we prove that selective semantic security and adaptive anonymity imply adaptive semantic security.

Mots clés: Identity-based encryption; selective/adaptive adversaries; semantic security; anonymity

Domaines: Informatique [cs]; Cryptographie et sécurité [cs.CR]

Javier Herranz, Fabien Laguillaumie, Carla Ràfols. Relations between semantic security and anonymity in identity-based encryption. Information Processing Letters, 2011, 111, pp.453 - 460. ⟨10.1016/j.ipl.2011.02.002⟩. ⟨hal-01084549⟩