Original title: Hidden Services Protocol for Mixnets
Nicolas Constantinides, Mahdi Rahimi, Stavros Nonis · September 2026
Mix networks, or mixnetsNetworks that shuffle messages through intermediaries to hide sender-receiver links., protect user privacy by sending data through intermediate computers called mixnodes. These mixnodes mix up, encrypt, and delay messages so outside spies cannot track who sent them. However, current mixnets do not securely hide the receiver's location from the sender. To fix this, researchers created a new hidden-service protocolA system that allows services to be accessed without revealing their network location.. It builds on tools called Single-Use Reply Blocks, or SURBsSingle-Use Reply Blocks, one-time addresses that let someone reply without knowing the receiver's address., which let receivers get replies without sharing their actual addresses. The team discovered two real-world attacks where an attacker who controls just a single mixnode can ruin this privacy, so they built defenses against both. Using these fixes, they built a system called NymHS. In tests browsing 118 websites, they proved hidden services work well on mixnets. Raising the message payload size from 2 KiB to 10 KiB made pages load about 5.2x faster on average and dropped network overhead from 21.7% to 4.3%.
Imagine you're sending secret letters through a chain of post offices that shuffle envelopes to hide who is writing to whom. The problem is that when the recipient replies, they have to send their address back, which could be traced if one post office worker is spying. Here, the researchers created untraceable reply slips and fixed the weakness so that even one bad worker can't break the secrecy.
For anyone who needs to host or access private online services, this means they can now do so without revealing their identity or location. Previously, an attacker controlling just one part of the network could break that privacy.
The abstract does not explicitly state limitations, but evaluation was done with web-browsing experiments across 118 websites, suggesting real-world testing. However, it does not address performance under all adversarial conditions, scalability beyond the tested configurations, or comparisons to other anonymity systems.
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Hidden Services Protocol for Mixnets — Nicolas Constantinides, Mahdi Rahimi, Stavros Nonis
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.