1 Department of Computer Science, Science and Technology, Aarhus University2 unknown3 Department of Computer Science, Science and Technology, Aarhus University
We present a constant-round unconditional black-box compiler that transforms any ideal (i.e., statistically-hiding and statistically-binding) straight-line extractable commitment scheme, into an extractable and equivocal commitment scheme, therefore yielding to UC-security . We exemplify the usefulness of our compiler by providing two (constant-round) instantiations of ideal straight-line extractable commitment based on (malicious) PUFs  and stateless tamper-proof hardware tokens , therefore achieving the first unconditionally UC-secure commitment with malicious PUFs and stateless tokens, respectively. Our constructions are secure for adversaries creating arbitrarily malicious stateful PUFs/tokens. Previous results with malicious PUFs used either computational assumptions to achieve UC-secure commitments or were unconditionally secure but only in the indistinguishability sense . Similarly, with stateless tokens, UC-secure commitments are known only under computational assumptions [13,24,15], while the (not UC) unconditional commitment scheme of  is secure only in a weaker model in which the adversary is not allowed to create stateful tokens. Besides allowing us to prove feasibility of unconditional UC-security with (malicious) PUFs and stateless tokens, our compiler can be instantiated with any ideal straight-line extractable commitment scheme, thus allowing the use of various setup assumptions which may better fit the application or the technology available.
Lecture Notes in Computer Science: 19th International Conference on the Theory and Application of Cryptology and Information Security, Bengaluru, India, December 1-5, 2013, Proceedings, Part II, 2013, p. 100-119