Paper 2014/691

Integration of hardware tokens in the Idemix library

Antonio de la Piedra

Abstract

The Idemix library provides the implementation of the Camenisch-Lysyanskaya (CL) Attribute-based Credential System (ABC), its protocol extensions and the U-Prove ABC. In the case of the CL ABC, the library can delegate some cryptographic operations to a hardware token (e.g. a smart card). In the last few years several practitioners have proposed different implementations of ABCs in smart cards. The IRMA card provides at the time of writing this manuscript, an optimal performance for practical applications. In this report, we address the case of integrating this implementation in the Idemix library. We opted for implementing the key binding use case together with the generation of exclusive scope pseudonyms and public key commitments on card. The integration requires two additional classes (one that parses system parameters, credential specifications and issuer public keys and other one that interfaces the card and its functionalities with the CL building block) together with one modification in the code if the signature randomization is delegated to the card (only required in one of the proposed alternatives). The integration of the key binding use case requires 540 bytes extra in the smart card. We can perform all the involved cryptographic operations in only 206.75 ms, including the computation of exclusive scope pseudonyms (55.19 ms).