Paper 2025/1374

An Attack to Universally Composable Commitments from Malicious Physically Uncloneable Functions and how to Avoid it

Abstract

In this work, we explore the possibility of unconditionally secure universally composable (UC) commitments, a very relevant cryptographic primitive in the context of secure multi-party computation. To this end, we assume the existence of Physically Uncloneable Functions (PUFs), a hardware security assumption that has been proven useful for securely achieving diverse tasks. In prior work [ASIACRYPT 2013, LNCS, vol. 8270, pp. 100–119] it was shown that a protocol for unconditional UC-secure commitments can be constructed even when the PUFs are malicious. Here, we report an attack to this protocol, as well as a few more issues that we identified in its construction. To address them, first we revise some of the previous PUF properties, and introduce new properties and tools that allow us to rigorously develop and present the security proofs. Second, we propose two different ways for making the commitment scheme secure against the attack we found. The first involves considering a new model where the creator of a PUF is notified whenever the PUF is queried and the second involves restricting adversaries to only being able to create stateless malicious PUFs. Finally, we analyze the efficiency of our schemes and show that our constructions are advantageous in this respect compared to the original proposal.