Cryptology ePrint Archive: Report 2015/104

Weakening the Isolation Assumption of Tamper-proof Hardware Tokens

Rafael Dowsley and Jörn Müller-Quade and Tobias Nilges

Abstract: Recent results have shown the usefulness of tamper-proof hardware tokens as a setup assumption for building UC-secure two-party computation protocols, thus providing broad security guarantees and allowing the use of such protocols as buildings blocks in the modular design of complex cryptography protocols. All these works have in common that they assume the tokens to be completely isolated from their creator, but this is a strong assumption. In this work we investigate the feasibility of cryptographic protocols in the setting where the isolation of the hardware token is weakened.

We consider two cases: (1) the token can relay messages to its creator, or (2) the creator can send messages to the token after it is sent to the receiver. We provide a detailed characterization for both settings, presenting both impossibilities and information-theoretically secure solutions.

Category / Keywords: Hardware Tokens, Isolation Assumption, UC security, One-Time Memory, Oblivious Transfer.

Original Publication (with major differences): ICITS 2015

Date: received 11 Feb 2015, last revised 30 Jun 2015

Contact author: rafael dowsley at kit edu

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Version: 20150630:152024 (All versions of this report)

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