When mixnets fail
Rahimi studies Loopix-like mixnets using Nym as the deployed case. Random independent path selection helps against a global network observer, but it also gives compromised mix nodes repeated chances to form a fully adversarial path as traffic volume grows.
Under the paper’s model, compromise of 10% or 5% of mix nodes could eliminate anonymity for clients sending more than approximately 4 or 30 megabytes to one destination. The paper proposes path-selection changes that reduce this risk while retaining much of the defense against a global passive observer.
The numerical thresholds are model-dependent, not measurements of a universal real-world break. The durable result is the tradeoff: the route randomization that frustrates one adversary can increase exposure to another adversary controlling relay nodes.