Mixnet
Also known as: mix network, mix net, mixnet routing, Chaumian mix
A mixnet, or mix network, is an anonymity system that collects messages from many senders into a batch, then reorders, delays, and re-encrypts them before forwarding, so an observer cannot link an incoming message to an outgoing one. Adding indistinguishable cover traffic further hides who is actually communicating. The technique, invented by David Chaum in 1981, specifically targets timing and traffic-correlation attacks that ordinary encryption leaves wide open.
Encryption hides what you say; a mixnet hides the fact that you said anything to a particular person. The core insight, from David Chaum's 1981 paper in Communications of the ACM, is that an adversary watching the network does not need to decrypt your traffic to deanonymize you. If a message leaves Alice at 14:32:07.1 and arrives at Bob 0.7 seconds later, over and over, the timing correlation alone proves they are talking, with greater than 99.99% confidence after enough samples.
A mix breaks that correlation by acting as a deliberate scrambler. It waits for a batch of messages from many senders, strips one layer of encryption from each, shuffles their order randomly, and only then releases them, often with added delay. Because every message entering the batch is the same size and indistinguishable on the wire, an observer watching both the input and output sees no way to match them up. Chaining several mixes together means no single node ever learns both the sender and the recipient.
Real-time mixnets also inject cover traffic, dummy messages that are byte-for-byte identical to real ones, so the network shows constant activity whether or not anyone is actually messaging. This defeats volume analysis and the idle-versus-active fingerprinting that timing delays alone cannot stop. See traffic analysis for the broader class of attacks mixnets defend against.
How it works
A simplified mix round:
1. Accumulate — collect messages from many senders during a randomized batch window. Each is padded to a single fixed size so lengths reveal nothing. 2. Inject cover — add dummy messages indistinguishable from real ones, keeping volume constant. 3. Shuffle — apply a Fisher-Yates random permutation so transmission order no longer reflects arrival order. 4. Delay and transmit — release messages one at a time with random inter-message delays drawn from a distribution that mimics natural network jitter. 5. Repeat across hops — chain multiple mixes so no single node sees both ends of a path.
Mixnet vs Tor: onion routing (Tor) is a low-latency design that forwards each packet immediately to stay fast for browsing and chat; it deliberately does not batch or delay, which leaves it vulnerable to end-to-end timing correlation by a global observer. A classic mixnet does batch, reorder, and delay, trading latency for much stronger resistance to timing analysis. The two are complementary, not competing: you can run mixnet-style batching on top of Tor circuits to get both IP-address anonymity and timing protection.
How RVNT uses Mixnet
RVNT layers a low-latency mixnet on top of its Tor circuits. In maximum-privacy mode it accumulates messages in randomized 500–2000 ms windows, injects 1–3 indistinguishable sealed sender cover envelopes per batch, Fisher-Yates-shuffles them, and transmits with random 50–200 ms inter-message delays. Idle cover traffic runs every 15–30 seconds to keep volume constant. Standard mode sends immediately with lighter cover traffic. Full mechanics and honest limits are in the mixnet docs.
Frequently asked questions
What is the difference between a mixnet and Tor?
Tor is a low-latency onion-routing network that forwards packets immediately to stay fast, which leaves it open to end-to-end timing correlation. A mixnet deliberately batches, reorders, and delays messages to break that correlation, trading speed for stronger anonymity. They are complementary: RVNT runs mixnet-style batching on top of Tor circuits to get both.
Can a mixnet make me completely anonymous?
No. A low-latency mixnet meaningfully raises the cost of deanonymization but cannot defeat a global passive adversary who watches all network traffic and correlates patterns over very large numbers of messages. It is a strong practical defense, not a mathematical guarantee, which is why RVNT documents its limits openly.
What is cover traffic and why do mixnets need it?
Cover traffic is dummy messages that look byte-for-byte identical to real ones, sent on a schedule whether or not you are actually messaging. It keeps your traffic volume constant so an observer cannot tell when you are active, defeating the volume and idle-versus-active analysis that timing delays alone cannot stop.
Every definition here describes something RVNT actually ships — a post-quantum, end-to-end-encrypted, peer-to-peer messenger with no phone number and no servers.