The Forgetful Disk Drive

Approaches to data protection have traditionally focused on physical security and/or cryptographic security, but the automatic deletion of data as a form of protection has not been widely employed. However, a vast amount of data is stored that has only a limited useful life and presents a risk to privacy and security after that time period. Approaches to data deletion can be broadly classified as physical destruction, data overwrite and cryptographic deletion. Cryptographic data deletion does not require any physical destruction and can be done quickly without any need to alter the data that is stored. Previous approaches to cryptographic data deletion have focused on bulk sanitization of storage devices. In this paper we introduce the notion of “forgetful” storage that employs cryptographic data deletion using a time-based approach to key management. By periodically erasing old keys and creating new keys, old data becomes automatically and instantly inaccessible, or virtually deleted. This data deletion can be accomplished without depending on any actions on the part of the user, application software or operating system. A refresh policy can be utilized to cause information that is accessed to be re-encrypted using a newer key, thereby extending the time before it will expire.