Security Seminar - Neekon Vafa

Security Seminar

Title: MacORAMa: Optimal Oblivious RAM with Integrity
Speaker: Neekon Vafa, Massachusetts Institute of Technology
Date: January 31
Time: 2:00 PM 
Location: Hybrid, Gates 403
Zoom Link

Abstract:
Oblivious RAM (ORAM), introduced by Goldreich and Ostrovsky (J. ACM '96), is a primitive that allows a client to perform RAM computations on an external database without revealing any information through the access pattern. For a database of size , well-known lower bounds show that a multiplicative overhead of in the number of RAM queries is necessary assuming client storage. A long sequence of works culminated in the asymptotically optimal construction of Asharov, Komargodski, Lin, and Shi (CRYPTO '21) with worst-case overhead and client storage. However, this optimal ORAM construction is known to be secure only in the honest-but-curious setting, where an adversary is allowed to observe the access patterns but not modify the contents of the database. In the malicious setting, where an adversary is additionally allowed to tamper with the database, this construction and many others in fact become insecure.In this work, we construct the first maliciously secure ORAM protocol with worst-case overhead and client storage assuming one-way functions, which are also necessary. By the ORAM lower bound, our construction is asymptotically optimal. We can also interpret our construction as an online memory checker that matches the bandwidth of the best known online memory checkers while additionally hiding the access pattern. To achieve this, we intricately interleave the ORAM construction of Asharov et al. with online and offline memory checking techniques.