We continue the line of work initiated by Katz (Eurocrypt 2007) on using tamper-proof hardware for universally composable secure computation. As our main result, we show an ecient oblivious-transfer (OT) protocol in which two parties each create and exchange a single, stateless token and can then run an unbounded number of OTs. Our result yields what we believe is the most practical and ecient known approach for oblivious transfer based on tamper-proof tokens, and implies that the parties can perform (repeated) secure computation of arbitrary functions without exchanging additional tokens. Motivated by this result, we investigate the minimal number of stateless tokens needed for universally composable OT/ secure computation. We prove that our protocol is optimal in this regard for constructions making black-box use of the tokens (in a sense we dene). We also show that nonblack-box techniques can be used to obtain a construction using only a single stateless token.
['Seung Geol Choi', 'Jonathan Katz', 'Dominique Schröder', 'Arkady Yerukhimovich', 'Hong-Sheng Zhou']
Efficient) Universally Composable Oblivious Transfer Using a Minimal Number of Stateless Tokens