The Power of the Differentially Oblivious Shuffle in Distributed Privacy Mechanisms [article]

Mingxun Zhou, Elaine Shi
2022 IACR Cryptology ePrint Archive  
The shuffle model has been extensively investigated in the distributed differential privacy (DP) literature. For a class of useful computational tasks, the shuffle model allows us to achieve privacy-utility tradeoff similar to those in the central model, while shifting the trust from a central data curator to a "trusted shuffle" which can be implemented through either trusted hardware or cryptography. Very recently, several works explored cryptographic instantiations of a new type of shuffle
more » ... h relaxed security, called differentially oblivious (DO) shuffles. These works demonstrate that by relaxing the shuffler's security from simulation-style secrecy to differential privacy, we can achieve asymptotical efficiency improvements. A natural question arises, can we replace the shuffler in distributed DP mechanisms with a DO-shuffle while retaining a similar privacy-utility tradeoff? In this paper, we prove an optimal privacy amplification theorem by composing any locally differentially private (LDP) mechanism with a DO-shuffler, achieving parameters that tightly match the shuffle model. Our result asymptoticaly improves the recent work of Gordon et al., who initiated the study of distributed DP mechanisms in the DO-shuffle model. Moreover, we explore multi-message protocols in the DO-shuffle model, and construct mechanisms for the real summation and histograph problems. Our error bounds approximate the best known results in the multi-message shufflemodel up to sub-logarithmic factors. Our results also suggest that just like in the shuffle model, allowing each client to send multiple messages is fundamentally more powerful than restricting to a single message.
dblp:journals/iacr/ZhouS22 fatcat:c37m3g5b2ze3dgdo2he6krumym