#network #peer #publish-subscribe #tor #zeromq


Wrapper for ZeroMQ's Pub-Sub with Curve+ZAP, over Tor. Peers, identified by public key, onion, and port, publish Vec<Vec<u8>> under topics to which other peers subscribe.

6 releases

0.9.10 Feb 2, 2024
0.9.8 Jan 8, 2024
0.9.6 Nov 30, 2023
0.9.4 Oct 31, 2023

#413 in Network programming

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logo disk Emyzelium (Rust)

is another wrapper around ZeroMQ's Publish-Subscribe messaging pattern with mandatory Curve security and optional ZAP authentication filter, over Tor, through Tor SOCKS proxy, for distributed artificial elife, decision making etc. systems where each peer, identified by its public key, onion address, and port, publishes and updates vectors of vectors of bytes of data under unique topics that other peers subscribe to and receive the respective data.

Requires Rust, libzmq (more on build, but e.g. libzmq3-dev and libzmq5 packages in Linux suffice), and Tor.

Versions in other languages:


There are tasks and scales where this model may succeed, seemingly (starting with pet-project-grade ones), and then there are tasks and scales where it will fail, miserably (ending with industry-, and especially critical-infrastructure-grade ones), up to the international day of mourning for its victims. Proceed with caution.

See also mycoses.


Let's use Emyzelium to introduce distributiveness into cellular automata, classical Conway's Life and its variations. Once... more... once... again...

For the sake of definiteness, Linux with installed Rust and libzmq5 package is assumed. But the demo should run under other OSes as well.

On single PC, connected to Internet

Are Tor and public key cryptography required to connect peers that reside in RAM of one and the same PC that you own? Of course not. However, before involving many computers, maybe you want to be sure that this thing can work in principle.

First of all, install Tor, to your Linux, and set up 3 hidden services on 3 different ports, arbitrary free ones above 1024. To be more precise, in your /etc/tor/torrc add lines like these:

HiddenServiceDir /var/lib/tor/p2p_dummysite1/
HiddenServicePort 60847

HiddenServiceDir /var/lib/tor/p2p_dummysite2/
HiddenServicePort 60848

HiddenServiceDir /var/lib/tor/p2p_dummysite3/
HiddenServicePort 60849

and in a terminal (note tor@default instead of tor):

$ sudo systemctl restart tor@default

then check if there are any problems:

$ systemctl status tor@default

should show ... active(running) ... and ... Bootstrapped 100% (done): Done ...

Wait a little for 3 specified dirs to appear, and, in each of them, the file hostname.

Now download Emyzelium files, say, to ~/emz-rs/, or simply by cargo install emyzelium. Open examples/demo.rs and, right after imports, change ALIEN_ONION value to onion address from /var/lib/tor/p2p_dummysite1/hostname without .onion suffix. Also change ALIEN_PORT value to 60847 if it is something else.

Make analogous changes to JOHN_ONION, JOHN_PORT (2) and MARY_ONION, MARY_PORT (3). Save changes to demo.rs.

You can also check whether these onion addresses have become known to Tor network; if they have, e.g. netcat should work, — open 2 terminals and see if it is the case:

term1$ nc -v -l 60847
term2$ torsocks nc -v ONION1.onion 60847

connection from ... and connected to ... means that onions are reachable. If they are not, wait for several minutes.

From ~/emz-rs/ build by

$ cargo build --release --example demo

Finally, to emyzeliumisation of Life. Open 3 terminals and from ~/emz-rs/ run the following in any order:

term1$ cargo run --release --example demo Alien
term2$ cargo run --release --example demo John
term3$ cargo run --release --example demo Mary

(Alternatively, run ./demo Name from ~/emz-rs/target/release/examples/.)

Then you should see something like this:

  • Terminal 1 (peer Alien):

Demo animation, Alien

  • Terminal 2 (peer John):

Demo animation, John

  • Terminal 3 (peer Mary):

Demo animation, Mary

As soon as Alien's, John's, and Mary's peers (efungi) have established connections (ehyphae) to each other over Tor, their cellular automatons (realms) can exchange cell regions (etales) not far from realtime.

Before the connections are established, SLUs (Since Last Update) are "large" (no updates yet); afterward they stay in 0–10 sec range. Press "1" or "2" to actually import updated region from other realm.

If you make that import automatic as well as emission, e.g. import from random other realm every 8 seconds, the process will become even more autonomous. Of course, in an environment so tiny, there is not much potential for evolution.

Note that birth/survival rules of Alien's CA, B34/S34, are different from classic B3/S23 of John's and Mary's CAs. In other words, although the "local geometry" of the realms is the same (Moore neigborhood), their "physics" are different.

The names "Alien", "John", "Mary" are not required and are used for convenience. Each peer is identified by its public key, onion, and port.

You can quit any of these 3 instances at any time and run it again after a while, the connections will be restored. The last "snapshot" of the region published by given peer is kept at each peer that has received it before being replaced by the next snapshot.

And you can mix versions in different languages, as long as no more than single instance of each peer runs at the same time. That is, you can replace

term1$ cargo run --release --example demo Alien


term1$ ./demo Alien

from Emyzelium in C++.

On multiple PCs connected to Internet

As it should be, the only principal difference from "Single PC" scenario is that hidden services are split between PCs. Let there be 3 of them, PC1 "Alien's", PC2 "John's", and PC3 "Mary's".

This time the port can be the same: on all 3 PCs, /etc/tor/torrc contains

HiddenServiceDir /var/lib/tor/p2p_dummysite/
HiddenServicePort 60847

only onion addresses in hostname files will be different and, as before, should be specified as ALIEN_ONION, JOHN_ONION, MARY_ONION values in demo.rs-s; all _PORT-s must be 60847. Also, this time it suffices on each PC to have in demo.rs only the single corresponding _SECRETKEY.

After Emyzelium files with accordingly modified demo.rs have been put on these PCs and demo executable has been successfully built, do the following:

pc1$ cargo run --release --example demo Alien
pc2$ cargo run --release --example demo John
pc3$ cargo run --release --example demo Mary

and almost exactly the same as above should be observed.

Security and keys

Emyzelium relies on ZeroMQ's Curve and ZAP encryption and authentication schemes, a variety of public key cryptography (basic knowledge of which is presumed). Therefore each "subject" within emyzelium needs and is partially defined by a secret key and a corresponding public key. There are 2 encodings of such keys: raw (32 bytes, each from 0–255 range) and printable Z85 (40 symbols, each from 85-element subset of ASCII).

Emyzelium's methods expect the keys as &str-s in Z85 encoding.

How to obtain such pair of keys
use std::ffi::{

#[link(name = "zmq")]
extern "C" {
    fn zmq_curve_keypair(z85_public_key: *mut c_char, z85_secret_key: *mut c_char) -> c_int;

const KEY_Z85_LEN: usize = 40;
const KEY_Z85_CSTR_LEN: usize = KEY_Z85_LEN + 1;

fn zmqe_curve_keypair() -> (String, String, i32) {
    let mut publickey_bufn = vec![0u8; KEY_Z85_CSTR_LEN];
    let mut secretkey_bufn = vec![0u8; KEY_Z85_CSTR_LEN];
    let r = unsafe {
            (&mut publickey_bufn).as_mut_ptr() as *mut c_char,
            (&mut secretkey_bufn).as_mut_ptr() as *mut c_char
    } as i32;
    (String::from_utf8(publickey_bufn[..KEY_Z85_LEN].to_vec()).unwrap(), String::from_utf8(secretkey_bufn[..KEY_Z85_LEN].to_vec()).unwrap(), r)

fn main() {
    let (publickey, secretkey, _) = zmqe_curve_keypair();
    println!("Public key: {}", &publickey);
    // Make sure no one is behind your back...
    println!("Secret key: {}", &secretkey);

Note Emyzelium is not used here; on the other hand, this very code is in examples/genkeypair.rs.

Obviously, keys are not arbitrary ASCII strings of length 40 that could be "typed by smashing on keyboard". In particular,

How to derive the public one from the secret one
#[link(name = "zmq")]
extern "C" {
    fn zmq_curve_public(z85_public_key: *mut c_char, z85_secret_key: *mut c_char) -> c_int;
    unsafe {
        secretkey.as_ptr().copy_to((&mut secretkey_bufn).as_mut_ptr(), KEY_Z85_LEN);
            (&mut publickey_bufn).as_mut_ptr() as *mut c_char,
            (&mut secretkey_bufn).as_mut_ptr() as *mut c_char
    println!("Public key: {}", String::from_utf8(publickey_bufn[..KEY_Z85_LEN].to_vec()).unwrap());

You construct peers with unique secret keys, one for each. No one except you or those whom you trust should know these keys. Anyone who wants to communicate with your peers must know the corresponding public keys. Accordingly, you must know the public keys of peers run by others if you want to communicate with them, in addition to their onion and port. Using "whitelist" feature (see below) based on ZAP, the owner of a peer can restrict those who are able to communicate with this peer.

Now we look closely at these

Entities, their roles and usage

In short, efunguz publishes etales, stretches out ehyphae to reach other efungi and receive etales that they publish (you should feel déjà vu here, because it is Synopsis with "mycological" metaphors).

All this throng of blobs better serve some purpose, — there are programs that need to be connected, to exchange data. We call such programs "realms" to emphasize that they may belong to very different environments, may be written in different languages, cannot be easily replaced all at once. Like two mushrooms in a forest, where one grows in a cave and the other at a river bank, but they are part of the same mycelium, efungi that you attach to each program communicate, and via efungi, "cave program" and "river bank program" communicate as well. See demo screencasts, Terminals 1–3.

Following the publish-subscribe pattern, Emyzelium model prefers "read" to "write": you cannot write some data to someone's program memory until they want to read it and do whatever they want with it, no one can write their data to the memory of your program unless you want to read that data and do whatever you want with it.

Another important property of this pattern is multicast: the data has no single intended recipient. Everyone who is allowed to subscribe to etales of your efunguz can receive any etale it publishes, if they know its title. Moreover, you do not know who actually received what etale, even if they received it at all, until they somehow communicate it back to you.

More on this below, but for now, consider these limitations and decide if they are compatible with your goals.

In case they do and one of your programs is in Rust, proceed. Otherwise, see S&B, this list etc.

Code snippets below assume

emyzelium = "X.Y.Z"


extern crate emyzelium;

use emyzelium::{self as emz, Efunguz};

See also demo.rs. In addition, it contains methods' calls with more arguments.

So, Efunguz, Ehypha, and Etale are just fancy names of well known concepts:

Efunguz, a.k.a. peer, is the mediator between some "realm", represented by your Rust program, and Tor network, represented by ZeroMQ on top of Tor SOCKS proxy, to which it talks. To the former, it simplifies security, (re)connection, and data flow tasks.

The simplest way to construct efunguz is

let my_secretkey: &str = "gbMF0ZKztI28i6}ax!&Yw/US<CCA9PLs.Osr3APc";
let mut efunguz = Efunguz::new(my_secretkey, & HashSet::new(), emz::DEF_PUBSUB_PORT, emz::DEF_TOR_PROXY_PORT, emz::DEF_TOR_PROXY_HOST);

More customisation:

let whitelist_publickeys = HashSet::from([String::from("WR)%3-d9dw)%3VQ@O37dVe<09FuNzI{vh}Vfi+]0"), String::from("iGxlt)JYh!P9xPCY%BlY4Y]c^<=W)k^$T7GirF[R")]);
let mut efunguz = Efunguz::new(my_secretkey, &whitelist_publickeys, 54321, 9955, emz::DEF_TOR_PROXY_HOST);

Now only the owners of secret keys corresponding to whitelist_publickeys will be able to subscribe to and receive etales of this efunguz. And they must connect to port 54321 instead of "default" one.

By default whitelist is empty, which means... opposite to what you might have thought: everyone is allowed to subscribe.

Efunguz is mutable. You can

  • add and delete keys from whitelist via add_whitelist_publickeys(), read_whitelist_publickeys() and del_whitelist_publickeys(), clear_whitelist_publickeys() methods of Efunguz object

  • add and delete ehyphae (see below) via add_ehypha() and del_ehypha():

let that_publickey: &str = "WR)%3-d9dw)%3VQ@O37dVe<09FuNzI{vh}Vfi+]0";
let that_onion: &str = "abcde23456abcde23456abcde23456abcde23456abcde23456abcdef";
let that_port: u16 = 12345;
if let Ok(ehypha) = efunguz.add_ehypha(that_publickey, that_onion, that_port) {
  • obtain immutable and mutable references to ehypha by its public key via get_ehypha() and get_mut_ehypha():
let that_publickey: &str = "iGxlt)JYh!P9xPCY%BlY4Y]c^<=W)k^$T7GirF[R";
if let Some(ehypha) = efunguz.get_ehypha(that_publickey) {
  • publish/emit etales via emit_etale():
let title: &str = "status2";
let parts: Vec<Vec<u8>> = vec![vec![2, 1], vec![255, 0, 2, 1]];
efunguz.emit_etale(title, &parts);

Title can be empty, "". It may be an agreement to publish some description of "normal" etales under empty title, so that other efungi will be able to obtain the list of (publicly) available etales:

 vec!["status2".as_bytes().to_vec(), "2B humidity, 4B kappa level".as_bytes().to_vec(),
  "advice".as_bytes().to_vec(), "C string with today's advice".as_bytes().to_vec()]);
  • update its state, ehyphae and their etales, using the data received from efungi it is connected to, via update()

The appropriate place to call update() from is the main loop of your program. Like this:

while !quit { // main program loop
    // do something here
    if my_status_updated {
        efunguz.emit_etale("status2", &status_parts);
    if that_etale.t_in() > t_last_etale {
        if (that_etale.parts.len() == 2) && (that_etale.parts[1].len() == 4) { // sanity checks
            let mut buf: [0u8; 4];
            buf.copy_from_slice(& that_etale.parts[1]);
            let kappa_level = i32::from_le_bytes(buf);
            // do something with kappa level
        t_last_etale = that_etale.t_in;
  • get the current count (hereafter denoted by IN1) of successfully authenticated incoming connections from other efungi, via in_absorbing_num()

  • get the total count (IN2) of successfully authenticated incoming connections, via in_permitted_num()

  • get the total count (IN3) of attempted incoming connections, via in_attempted_num()

Most of the time, IN1IN2 because some efungi might have disconnected, and IN2IN3 because some efungi might have not even passed authentication filter.

See also Realm_CA::run() in demo.rs.

Internally, Efunguz owns ZeroMQ context, PUB socket for etales, REP socket for ZAP authentication, and PAIR socket monitoring PUB.

Ehypha, a.k.a. the connection from one efunguz to another. Via ehypha, the former receives etales from the latter. It is a part of Efunguz, thus its construction was considered above.

Ehypha is mutable. You can

  • subscribe and unsubscribe to etales from target efunguz via add_etale() and del_etale():
if let Ok(that_etale) = ehypha.add_etale("status3") {

At first, etale is empty (no parts). If efunguz with public key WR)%3-d9dw)%3VQ@O37dVe<09FuNzI{vh}Vfi+]0 is available at onion abcde23456abcde23456abcde23456abcde23456abcde23456abcdef, port 12345, allows subscriptions from your efunguz, and publishes etale under the title status3, then, after a while, this etale will be received by you after efunguz.update() call, and will be updated as long as these conditions hold. Its fields are described below in Etale paragraph.

  • obtain immutable reference to etale by its title via get_etale():
let title: &str = "status7";
if let Some(etale) = ehypha.get_etale(title) {
  • pause and resume update of either single etale, or all etales, via pause_etale[s]() and resume_etale[s]()

Internally, Ehypha owns SUB socket for etales. The context is the one of Efunguz.

Etale, a.k.a. partitioned data chunk with metadata, is the main data unit that efungi exchange. It has the following public methods to access its read-only fields:

  • parts() -> & Vec<Vec<u8>> is the latest obtained data

  • t_out() -> i64 is the time in microseconds since Unix epoch, measured at sender, when the etale was published

  • t_in() -> i64 is the time in microseconds since Unix epoch, measured at receiver, when the etale was obtained

Etale is immutable from outside and is owned by Ehypha from which it was constructed.

Let "tale" in the name remind that a tale may be a lie, regardless of intentions of a teller or expectations of a listener.

The main data flow then is

Realm 1 ↔ Efunguz 1 ↔ ZeroMQ ↔ Tor ↔ turtles ↔ Tor ↔ ZeroMQ ↔ Efunguz 2 ↔ Realm 2

Here it is bidirectional, but may be unidirectional as well. For this to work, each efunguz must know network addresses of all efungi it gathers etales from, that is, of efungi to which its ehyphae are connected. This is where onions of Tor network come in...

...before v0.9.0, there were Ecataloguzes a.k.a. nameservers, Efungi talked to them exchanging their (dynamic) IP addresses, and Emyzelium worked over basic TCP/IP Internet... or rather would work were there no NATs, firewalls etc. (It actually worked — inside LAN only :) Now, because Tor solves this problem, we do not have to write here another boring section on those nameservers! Also, さよなら port forwarding, hole punching et al.

PAQ (Potentially Asked Questions)

Q. What novelty does Emyzelium introduce in comparison with other similar projects?

A. IOHO, none.

Q. How reliable Emyzelium is? How secure? Are there backdoors?

A. No "audit" has been performed, so... read the source through carefully, it is small enough — Rust version is smaller than this README. The buck then goes to underlying layers — ZeroMQ, Curve, Tor, TCP/IP, BIOS/EFI, hardware etc. Sorry, there is no other way if you trust only yourself of current Planck time unit.

Yes, there are backdoors. No, there are no backdoors.

Do not omit sanity checks of received etales and during their deserialisation.

Do not use keys from demo, generate your own unique pairs.

Q. Emyzelium is crap, I will never use it, but I want to exchange data with some efungi. What do I need in addition to their onions, ports, and public keys?

A. There is nothing "Emyzelium-specific" in the data that flows between the entities described here. You subscribe to some null-terminated topic on "publisher" port of Efunguz? — It will send corresponding etale to you, if there is no whitelist or you are in it. Write your own/use written by someone wrapper around the parts of ZeroMQ, Tor etc. that you need (cf. STREAM sockets). In fact, Emyzelium implementation of Emyzelium (or whatever traditional name it has) architecture is here already. And to exchange data with emyzelium is to be its part. If the data then goes somewhere else, maybe you aim at a bridge. After all, you can always rewrite it from scratch or improve what causes your antipathy, rename to "Epór"/"Ekinzhitai"/"E..." (based on "mycelium" in Irish/Japanese/...) and use that.

Q. Some scoundrels are using emyzelium to commit bad things. How can they be stopped?

A. Nothing special for such architectures, probably. Restrict access to Tor, identify devices that participate in the network... some metadata analysis... and there are areas beside mycology.

Q. Some scoundrels are shutting down emyzelium we use to commit good things. How can they be stopped?

A. Nothing special for such architectures, probably. Use Tor bridges, switch devices that participate in the network... some metadata obfuscation... and there are areas beside mycology.


Mostly big ones...


This wrapper is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This wrapper is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.