Mix network

This breaks the link between the source of the request and the destination, making it harder for eavesdroppers to trace end-to-end communications.

Large-scale implementations of the mix network concept began to emerge in the 2020s, driven by advancements in privacy-preserving technologies and decentralized infrastructure[6].

David Chaum published the concept of Mix Networks in 1979 in his paper: "Untraceable electronic mail, return addresses, and digital pseudonyms".

While public key cryptography encrypted the security of information, Chaum believed there to be personal privacy vulnerabilities in the meta data found in communications.

Innovators like Ian Goldberg and Adam Back made huge contributions to mixnet technology.

This era saw significant advancements in cryptographic methods, which were important for the practical implementation of mixnets.

Mixnets began to draw attention in academic circles, leading to more research on improving their efficiency and security.

However, widespread practical application was still limited, and mixnets stayed largely within experimental stages.

A "cypherpunk remailer" software was developed to make it easier for individuals to send anonymous emails using mixnets.

[7] In the 2000s, the increasing concerns about internet privacy highlighted the significance of mix networks (mixnets).

This period also witnessed the emergence of other systems that incorporated mixnet principles to various extents, all aimed at enhancing secure and anonymous communication.

This change was driven by the introduction of new protocols and algorithms, which helped overcome some of the primary challenges that had previously hindered the widespread deployment of mixnets.

The relevance of mixnets surged, especially after 2013, following Edward Snowden's disclosures about extensive global surveillance programs.

The Loopix[8] architecture, introduced in 2017, integrated several pre-existing privacy-enhancing techniques to form a modern mix network design.

Key elements of Loopix included: The rise of blockchain technologies opened new possibilities for scalable decentralized systems, paving the way for large-scale, distributed mix networks.

Throughout the 2020s, various public and private research and development programs contributed to the realization of the first large-scale mix networks.

By 2025, multiple projects[6]—including 0KN, HOPR, Katzenpost, Nym, and xx.network (led by David Chaum)—are under active development, aiming to enhance privacy-preserving communication on a broader scale.

[citation needed] On one hand, it brings new challenges, because quantum computers are very powerful and could break some of the current security methods used in mixnets.

This will help make sure that mixnets can keep offering strong privacy and security even as technology changes and grows.

Upon receipt of the encrypted top-level envelope, the mix uses its secret key to open it.

The following indicates how B uses this untraceable return address to form a response to A, via a new kind of mix: The message from A

Adversaries can provide long term correlation attacks and track the sender and receiver of the packets.

[10] An adversary can perform a passive attack by monitoring the traffic to and from the mix network.

Sequences of inter-packet interval vary greatly between connections, for example in web browsing, the traffic occurs in bursts.

Active attacks can be performed by injecting bursts of packets that contain unique timing signatures into the targeted flow.

The attacker might not be able to create new packets due to the required knowledge of symmetric keys on all the subsequent mixes.

This is done by creating a signature from artificial packets by holding them on a link for a certain period of time and then releasing them all at once.

The attacker can actively modify packet streams to observe the changes caused in the network's behavior.

From this, the attacker can learn the received message could not have come from the sender into any layer 1 mix that did not fire.

There is a higher probability of matching the sent and received messages with these sleepers thus communication is not completely anonymous.