Zero Knowledge Systems

Abstract: We present the traffic analysis problem and expose the most important protocols, attacks and design issues. Afterwards, we propose directions for further research. As we are mostly interested in efficient and practical Internet based protocols, most of the emphasis is placed on mix based constructions. The presentation is informal in that no complex definitions and proofs are presented, the aim being more to give a thorough introduction than to present deep new insights.

Abstract: In this paper we show how to convert a statistically binding but computationally concealing quantum bit commitment scheme into a computationally binding but statistically concealing QBC scheme. For a security parameter n, the construction of the statistically concealing scheme requires O(n2) executions of the statistically binding scheme. As a consequence, statistically concealing but computationally binding quantum bit commitments can be based upon any family of quantum one-way functions. Such a construction is not known to exist in the classical world.

Abstract: We describe a weakness in the High Bandwidth Digital Content Protection (HDCP) scheme which may lead to practical attacks. HDCPi s a proposed identity-based cryptosystem for use over the Digital Visual Interface bus, a consumer video bus used to connect personal computers and digital display devices. Public/private key pairs are assigned to devices by a trusted authority, which possesses a master secret. If an attacker can recover 40 public/private key pairs that span the module of public keys, then the authority's master secret can be recovered in a few seconds. With the master secret, an attacker can eavesdrop on communications between any two devices and can spoof any device, both in real time. Additionally, the attacker can produce new key pairs not on any key revocation list. Thus the attacker can completely usurp the trusted authority's power. Furthermore, the protocol is still insecure even if all devices' keys are signed by the central authority.

Abstract: We discuss tradeoffs between privacy and other attributes such as security, usability, and advances in technology We discuss whether such tradeoffs are inherent, or if it is possible to "have it all"