When a Threshold Mix accumulates a given number of messages, it outputs a randomly subset of messages

In a Mix, if all messages have different sizes an attacker can correlate input with output messages

Supose that in a TOR network composed of 880, an

attacker has gained control of 814. With what probability can the

attacker correlate traffic in the network?

A common anonymity measure in a communication is the cardinality of the anonymity set

A partial adversary has access to the whole communication links

Supose that in a TOR network composed of 353, an

attacker has gained control of 168. With what probability can the

attacker correlate traffic in the network?

To improve the anonymity measure based on the anonymity set, we can use its entropy instead of it cardinality

An active adversary is the one who can only listen (observe) a communication

A Crowds system protects against a passive and local adversaries

In a Crowds system with N nodes (jondos) and forwarding probability p, the maxim path length that a message will use (that is, path of crowd nodes before reachin the destination) is n-p