HP Labs Technical Reports

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Blind Certification of Public Keys and Efficiently Revocable Cash: Secure Against Capable Attackers

Mao, Wenbo


Keyword(s): electronic cash; blind certification of public keys; revocation; cryptography

Abstract: Electronic cash should be revocable in order to nullify the effect of attacks mounted by a capable attacker (e.g. double spending by reverse-engineering tamper- resistant devices). For prudent engineering considerations, cash revocability forms a necessary complementary measure to using tamper-resistant devices, adding system security while lowering system cost by reducing the level of physical tamper resistance required. We propose a revocable cash scheme. Cash revocation is achieved efficiently via withdrawing an attacker's ability to further use the system. In several ways the new scheme improves from previous ones (including trustee-based tracing techniques, e.g., [5, 14, 19]), that identify the attacker and revoke cash in terms of publishing a blacklist of coins misused or robbed. Firstly, the new scheme can stop the attacker from further using the system without need of physical confiscation of him/her or his/her devices (physical confiscation is difficult over the network). Secondly, it will achieve a better performance due to avoiding real-time checking through a potentially big coin revocation list. Thirdly, without using trustee, the system serves unconditional privacy for honest users and uses simpler protocols for transactions.

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