Unconditional and Composable Security Using a Single Stateful Tamper-Proof Hardware Token

Abstract

Abstract. Cryptographic assumptions regarding tamper proof hardware tokens have gained increasing attention. Even if the tamperproof hardware is issued by one of the parties, and hence not necessarily trusted by the other, many tasks become possible: Tamper proof hardware is sufficient for universally composable protocols, for informationtheoretically secure protocols, and even allow to create software which can only be used once (One-Time-Programs). However, all known protocols employing tamper-proof hardware are either indirect, i.e., additional computational assumptions must be used to obtain general two party computations or a large number of devices must be used. In this work we present the first protocol realizing universally composable two-party computations (and even trusted One-Time-Programs) with informationtheoretic security using only one single tamper-proof device issued by one of the mutually distrusting parties.

Unconditionally Secure and Universally Composable Commitments from Physical Assumptions

“…A consequence of this model is that the security of a player now depends only on its own token being good and holds even if tokens used by other players are not genuine! This new setup assumptions has gained a lot of interest and several works after [27] have shown that unconditional UC-security is possible [32,25], even using a single stateful token [22,23]. Note that a stateful token, in contrast with a stateless token, requires an updatable memory that can be subject to reset attacks.…”

(Efficient) Universally Composable Oblivious Transfer Using a Minimal Number of Stateless Tokens

“…Our protocols are thus optimal in this regard. Note that a single stateful token suffices for universally composable OT [20]; our result thus demonstrates a separation between stateful and stateless tokens.…”

“…Goyal et al [29] show an unconditional construction of oblivious transfer (and hence general secure computation) using Θ(λ) stateful tokens. Döttling et al [20] show how to construct unconditionally secure OT using only a single stateful token. Goyal et al [28] showed that unconditional security from stateless tokens is impossible unless the token model is extended to allow Table 1: Universally composable OT based on stateless tamper-proof hardware tokens.…”

“…Our starting point is the unconditionally secure OT protocol from [20], which uses a single stateful token. We sketch a simplified version of their protocol for the case of a single OT carried out between the sender S with input (x 0 , x 1 ) ∈ {0, 1} λ × {0, 1} λ and the receiver R with input b ∈ {0, 1}.…”

“…In addition to introducing the model, Katz showed that tamper-proof hardware tokens can be used for universally composable computation of arbitrary functions under additional cryptographic assumptions. His work motivated an extensive amount of follow-up work [13,47,26,16,28,29,20] that we discuss in detail later.…”