Large universe subset predicate encryption achieves constant size and CCA security
Large Universe Subset Predicate Encryption with IND-CCA Security (with Constant-size Ciphertext and Keys)
Cryptography and Security
Summary
Securely controlling who can read encrypted data can be tricky when there are many users and different access rules. Previous methods for a system called subset predicate encryption either had big secret keys and messages or weaker security. The authors designed a new, more secure version that keeps secret keys and encrypted messages small, even when handling a large number of users. They also showed how to build other secure encryption systems using their approach.
What this means in practice
- •For security engineers: Implement efficient encryption systems that manage large user sets with strong protection against adaptive attacks and minimal key and ciphertext sizes.
- •For cloud service developers: Build scalable access control encryption for cloud data that supports complex user subsets with constant-size encryptions and keys.
Authors
Sayantan Mukherjee
Abstract
Katz et al. (CANS'17) introduced Subset Predicate Encryption (SPE). This scheme is a generalization of broadcast encryption as it emulates the \emph{subset containment} predicate in the encrypted domain. They proposed two selectively IND-CPA secure SPE constructions in the small universe setting. They also showed some black-box transformations of SPE to well-known primitives like WIBE and ABE to establish the richness of the SPE structure. Chatterjee and Mukherjee (RSA'19) proposed two SPE constructions in the large-universe setting. Their first construction achieved constant-size ciphertexts and secret keys, but it is proven secure in a restricted version of selective security. Although the second construction achieves adaptive security, the ciphertext size depends on the size of the data-attribute set. Furthermore, neither of these two constructions achieves CCA security. In this work, we propose the first large-universe CCA-secure subset predicate encryption with constant-size ciphertext and secret keys. We prove this construction achieves standard selective security under the standard subgroup decision problems. Finally, we transform our extremely efficient SPE into the first CCA-secure WIBE, WKD-IBE, etc., with constant-size ciphertexts and secret keys via black-box transformations.