# Types for Location and Data Security in Cloud Environments

## TL;DR

This paper introduces a typed programming language for cloud environments that enforces data access policies across devices, ensuring confidentiality even with untrusted or compromised devices, without requiring a centralized PKI.

## Contribution

It presents a novel type system that guarantees data confidentiality and policy enforcement in distributed cloud systems without middleware or pre-registered identities.

## Key findings

- Type system enforces data access restrictions across devices.
- Confidentiality holds against any intruder under labeled bisimilarity.
- Programming errors do not lead to data leakage in well-typed devices.

## Abstract

Cloud service providers are often trusted to be genuine, the damage caused by being discovered to be attacking their own customers outweighs any benefits such attacks could reap. On the other hand, it is expected that some cloud service users may be actively malicious. In such an open system, each location may run code which has been developed independently of other locations (and which may be secret). In this paper, we present a typed language which ensures that the access restrictions put on data on a particular device will be observed by all other devices running typed code. Untyped, compromised devices can still interact with typed devices without being able to violate the policies, except in the case when a policy directly places trust in untyped locations. Importantly, our type system does not need a middleware layer or all users to register with a preexisting PKI, and it allows for devices to dynamically create new identities. The confidentiality property guaranteed by the language is defined for any kind of intruder: we consider labeled bisimilarity i.e. an attacker cannot distinguish two scenarios that differ by the change of a protected value. This shows our main result that, for a device that runs well typed code and only places trust in other well typed devices, programming errors cannot cause a data leakage.