Harnessing data loss with forgetful data structures

Forgetting, losing, or corrupting data is almost universally considered harmful in computer science and blasphemous in database and file systems. Typically, loss of data is a consequence of unmanageable or unexpected lower layer deficiencies that the user process must be protected from through multiple layers of storage abstractions and redundancies. We argue that forgetfulness can be a resource for system design and that, like durability, security or integrity, can be used to achieve uncommon, but potentially important goals such as privacy, plausible deniability, and the right to be forgotten. We define the key properties of forgetfulness and draw inspiration from human memory. We develop a data structure, the forgit, that can be used to store images, audio files, videos or numerical data and eventually forget. Forgits are a natural data store for a multitude of today's cloud-based applications and we discuss their use, effectiveness, and limitations in this paper.