Data is increasingly collected and shared, with potential benefits for both individuals and society as a whole, but people cannot always be confident that their data will be shared and used appropriately. Decisions made with the help of sensitive data can greatly affect lives, so there is a need for ways to hold data processors accountable. This requires not only ways to audit these data processors, but also ways to verify that the reported results of an audit are accurate, while protecting the privacy of individuals whose data is involved.
We (Alexander Hicks, Vasilios Mavroudis, Mustafa Al-Basam, Sarah Meiklejohn and Steven Murdoch) present a system, VAMS, that allows individuals to check accesses to their sensitive personal data, enables auditors to detect violations of policy, and allows publicly verifiable and privacy-preserving statistics to be published. VAMS has been implemented twice, as a permissioned distributed ledger using Hyperledger Fabric and as a verifiable log-backed map using Trillian. The paper and the code are available.
Use cases and setting
Our work is motivated by two scenarios: controlling the access of law-enforcement personnel to communication records and controlling the access of healthcare professionals to medical data.
The UK Home Office states that 95% of serious and organized criminal cases make use of communications data. Annual reports published by the IOCCO (now under the IPCO name) provide some information about the request and use of communications data. There were over 750 000 requests for data in 2016, a portion of which were audited to provide the usage statistics and errors that can be found in the published report.
Not only is it important that requests are auditable, the requested data can also be used as evidence in legal proceedings. In this case, it is necessary to ensure the integrity of the data or to rely on representatives of data providers and expert witnesses, the latter being more expensive and requiring trust in third parties.
In the healthcare case, individuals usually consent for their GP or any medical professional they interact with to have access to relevant medical records, but may have concerns about the way their information is then used or shared. The NHS regularly shares data with researchers or companies like DeepMind, sometimes in ways that may reduce the trust levels of individuals, despite the potential benefits to healthcare.