Commune: Shared Ownership in an Agnostic Cloud

TL;DR

Commune introduces a method for shared ownership in cloud storage, enabling collaborative access control without modifying existing cloud platforms, and ensuring access requires consensus among owners.

Contribution

It formally defines shared ownership in cloud access control and proposes a distributive enforcement solution compatible with existing clouds like Amazon S3.

Findings

Secure shared ownership enforcement demonstrated

Scalable performance on Amazon S3

No modifications needed for existing cloud platforms

Abstract

Although cloud storage platforms promise a convenient way for users to share files and engage in collaborations, they require all files to have a single owner who unilaterally makes access control decisions. Existing clouds are, thus, agnostic to shared ownership. This can be a significant limitation in many collaborations because one owner can, for example, delete files and revoke access without consulting the other collaborators. In this paper, we first formally define a notion of shared ownership within a file access control model. We then propose a solution, called Commune, to the problem of distributively enforcing shared ownership in agnostic clouds, so that access grants require the support of a pre-arranged threshold of owners. Commune can be used in existing clouds without requiring any modifications to the platforms. We analyze the security of our solution and evaluate its scalability and performance by means of an implementation integrated with Amazon S3.