Paper 2021/867

Key-Policy ABE with Delegation of Rights

Cécile Delerablée and Lénaïck Gouriou and David Pointcheval

Abstract

This paper revisits Key-Policy Attribute-Based Encryption, allowing the delegation of keys, traceability of compromised keys and key anonymity, as additional properties. Whereas delegation of rights has been addressed in the seminal paper by Goyal et al. in 2006, introducing KPABE, this nice feature has almost been neglected in all subsequent works in favor of better security levels. However, in multi-device scenarios, this is quite important to allow users to independently authorize their own devices, still with some tracing capabilities and some anonymity properties. To this aim, we define a new primitive with switchable attributes, in both the ciphertexts and the keys, and new indistinguishability properties. We then provide concrete and efficient instantiations with adaptive security under the sole SXDH assumption in the standard model.