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Anonymity Set

Classification Key : Exterior Security, Information Disclosure


Batched Routing works best for systems with stable traffic patterns. But many application domains do not have stable traffic. Low-latency mixes cannot indefinitely wait for incoming traffic. A VANET or a location-based anonymity solution has no control on the movement of an agent. Systems with variable number of users and with changing traffic conditions may result in low levels of anonymity. An attacker can also take advantage by launching a denial of service attack on the incoming channel of a mix, and force it to drop its stale traffic.
How can a node be implemented to operate without depending on external sources to create anonymity cover?


Add random delays to make a system non-deterministic. Keep a packet in the pool, and forward it immediately after the delay is passed.

Known Uses

In a system following random wait strategy, the delay is independent of the network traffic. Hence, tight delay constraints can be implemented by a mix, regardless of the current load. It is useful for systems for which low latency is more important than providing a high level of anonymity, e.g., web browsers. Unlike a batched mix, the anonymity level may become low when traffic level drops. However, there is always a tradeoff between delay and anonymity for low-latency systems.
A VANET has no control over the agents. However, it surrounds a mix zone with another region, typically a road intersection, where the agents go through a silent period. The transmission is disabled for a random time in the silent zone.

Related Patterns

Cover Traffic


Hafiz Privacy Patterns


Anonymity, Privacy


Last modified: May 05, 2012

Conceived and Maintained by: Munawar Hafiz