Volunteer Computing is becoming a new paradigm not only for the Computational Grid, but also for institutions using production-level Data Grids because of the enormous storage potential that may be achieved at a low cost by using commodity hardware within their own computing premises. However, this novel “Desktop Data Grid” depends on a set of widely distributed and untrusted storage nodes, therefore offering no guarantees about neither availability nor protection to the stored data. These security challenges must be carefully managed before fully deploying Desktop Data Grids in sensitive environments (such as eHealth) to cope with a broad range of storage needs, including backup and caching.
In this paper we propose a cryptographic protocol able to fulfil the storage security requirements related with a generic Desktop Data Grid scenario, which were identified after applying an analysis framework extended from our previous research on the Data Grid’s storage services. The proposed protocol uses three basic mechanisms to accomplish its goal: (a) symmetric cryptography and hashing, (b) an Information Dispersal Algorithm and the novel (c) “Quality of Security” (QoSec) quantitative metric. Although the focus of this work is the associated protocol, we also present an early evaluation using an analytical model. Our results show a strong relationship between the assurance of the data at rest, the QoSec of the Volunteer Storage Client and the number of fragments required to rebuild the original file.