Existing techniques for expiration of data Sample Clauses

Existing techniques for expiration of data. Xxxxx-Xxxxxxxxxxx [1] discusses the broad consequences of the virtually unbounded memory in current information systems. He proposes to tag sensitive data with an expiration date and to require all servers handling such data to obey that date. Such a mandate conflicts with the business interests of many corporate information service providers, and with the interests of governments. A word-wide legal mandate to respect data expiration dates, on the other hand, seems out of reach in the foreseeable future. Moreover, it is technically difficult to verify that all servers actually delete the data and hold delinquent service providers accountable. In recent years, a number of research projects have sought to address various aspects of this problem. In a first line of work, the expiration date associated with personal data is implemented by encrypting the data itself with a symmetric encryption key and restricting access to these keys. Unfortunately, none of these systems are capable of dealing with scenarios where published data is subsequently manipulated, e.g., re-encoding of JPEGs as commonly done in social networks such as Facebook. Similarly, the challenges of storing and distributing keys securely during their period of validity has not been considered thus far. Finally, preventing unauthorized copying, notifying all key holders to delete their keys, and authenticating removal requests remain open problems. One line of work is aimed at effectively closed systems, such as corporate information systems and systems limited to a single jurisdiction. Here, all servers are aware of the encrypted nature of the data, post-processing of data is not supported, and the threat of an adversary who obtains keys while the data is available is generally not considered. The first such system we are aware of is described in [2], which provided the basic principle. Another prominent system is the Ephemerizer [3], an improved version of which was later described in [4]. Vanish [5] is a more recent approach, which stores shares of the keys in a distributed hash table (DHT), a data structure that underlies P2P networks. The DHT is designed to reliably remove the key after a certain time, so that the cleartext data becomes unavailable (although encrypted copies may persist). An attack against the proposed implementation was recently published [6], using a Xxxxx attack on the DHT.