Anonymous RAM

Michael Backes, Amir Herzberg, Aniket Kate, Ivan Pryvalov

Abstract: We define the concept of and present provably secure constructions for Anonymous RAM (AnonRAM), a novel multi-user storage primitive that offers strong privacy and integrity guarantees. AnonRAM combines privacy features of anonymous communication and oblivious RAM (ORAM) schemes, allowing it to protect, simultaneously, the privacy of content, access patterns and user’s identity, from curious servers and from other (even adversarial) users. AnonRAM further protects integrity, i.e., it prevents malicious users from corrupting data of other users. We present two secure AnonRAM schemes, differing in design and time complexity. The first scheme has a simpler design; like efficient ORAM schemes, its time complexity is poly-logarithmic in the number of cells (per user); however, it is linear in the number of users. The second AnonRAM scheme reduces the overall complexity to poly-logarithmic in the total number of cells (of all users) at the cost of requiring two (non-colluding) servers.