Access Control Encryption: Enforcing Information Flow with Cryptography

TL;DR

This paper introduces Access Control Encryption (ACE), a new cryptographic primitive enabling fine-grained control over message sending and receiving rights, inspired by classical security models like Bell-Lapadula.

Contribution

It formally defines ACE and provides two constructions: one with linear complexity based on number theoretic assumptions, and another with polylogarithmic complexity using cryptographic obfuscation.

Findings

First formal definition of ACE as a cryptographic primitive.

Construction with linear complexity based on DDH and Paillier assumptions.

Efficient construction with polylogarithmic complexity using cryptographic obfuscation.

Abstract

We initiate the study of Access Control Encryption (ACE), a novel cryptographic primitive that allows fine-grained access control, by giving different rights to different users not only in terms of which messages they are allowed to receive, but also which messages they are allowed to send. Classical examples of security policies for information flow are the well known Bell-Lapadula [BL73] or Biba [Bib75] model: in a nutshell, the Bell-Lapadula model assigns roles to every user in the system (e.g., public, secret and top-secret). A users' role specifies which messages the user is allowed to receive (i.e., the no read-up rule, meaning that users with public clearance should not be able to read messages marked as secret or top-secret) but also which messages the user is allowed to send (i.e., the no write-down rule, meaning that a user with top-secret clearance should not be able to write messages marked as secret or public). To the best of our knowledge, no existing cryptographic primitive allows for even this simple form of access control, since no existing cryptographic primitive enforces any restriction on what kind of messages one should be able to encrypt. Our contributions are: - Introducing and formally defining access control encryption (ACE); - A construction of ACE with complexity linear in the number of the roles based on classic number theoretic assumptions (DDH, Paillier); - A construction of ACE with complexity polylogarithmic in the number of roles based on recent results on cryptographic obfuscation;