Encrypted Shared Data Spaces

The deployment of Share Data Spaces in open, possibly hostile, environments arises the need of protecting the confidentiality of the data space content. Existing approaches focus on access control mechanisms that protect the data space from untrusted agents. The basic assumption is that the hosts (and their administrators) where the data space is deployed have to be trusted. Encryption schemes can be used to protect the data space content from malicious hosts. However, these schemes do not allow searching on encrypted data. In this paper we present a novel encryption scheme that allows tuple matching on completely encrypted tuples. Since the data space does not need to decrypt tuples to perform the search, tuple confidentiality can be guaranteed even when the data space is deployed on malicious hosts (or an adversary gains access to the host). Our scheme does not require authorised agents to share keys for inserting and retrieving tuples. Each authorised agent can encrypt, decrypt, and search encrypted tuples without having to know other agents’ keys. This is beneficial inasmuch as it simplifies the task of key management. An implementation of an encrypted data space based on this scheme is described and some preliminary performance results are given

Coordination with Multicapabilities

In the context of open distributed systems, the ability to coordinate agents coupled with the possibility to control the actions they perform is important. As open systems need to be scalable, capabilities may provide the best-fit solution to overcome the problems caused by the loosely controlled coordination of tuple-space systems. Acting as a ‘ticket’, capabilities can be given to the chosen agents, granting them different privileges over different kinds of data—thus providing the system with a finer control on objects’ visibility to agents. One drawback of capabilities is that they can only refer to named objects—something that is not universally applicable since, unlike tuple-spaces, tuples are nameless. This paper demonstrates how the advantages of capabilities can be extended to tuples, with the introduction of multicapabilities, which generalise capabilities to collections of objects. We also present discussions on implementation and application examples to illustrate the use of capabilities and multicapabilities in tuple-space systems