Paper 2021/867 Original: eprint.iacr.org/2021/867 ↗

Key-Policy ABE with Switchable Attributes

Abstract

This paper revisits Key-Policy Attribute-Based Encryption (KP-ABE), allowing dele- gation 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 KP-ABE, this 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, and thus to delegate their initial rights with possibly more restrictions to their everyday-use devices. But then, one may also require tracing capabilities in case of corrupted devices and anonymity for the users and their devices. To this aim, we define a new variant of KP-ABE including delegation, with switchable attributes, in both the ciphertexts and the keys, and new indistinguishability properties. We then provide a concrete and efficient instantiation with adaptive security under the sole SXDH assumption in the standard model. We eventually explain how this new primitive can address all our initial goals.