Byzcoin is a high-performance permissioned blockchain that can safely run in public mode, meaning everybody with access tokens can use it. It is developed by the DEDIS lab at EPFL and supported by the C4DT. Novel parts of the byzcoin blockchain are the DARC structures that allow delegation of access control and decentralized management. Another new part is Calypso which allows to encrypt to a set of servers and define access control to users who will be able to decrypt the data.

In this README you will find a short explanation how you can get a node up and running to join the DEDIS byzcoin test-net. For a more technical description, see one of:

• Why this repository
• Collective Authority Project
• ByzCoin Paper
• Security Assessment

To run a byzcoin node, you need a server with 2GB of RAM, 10GB of harddisk, and a CPU not older than 5 years. The simplest way to run your node is using docker. If you want to compile from source, or use the binary, please have a look at more setups.

wget https://raw.githubusercontent.com/c4dt/byzcoin/master/docker-compose.yml
# Edit ADDRESS_* and DESCRIPTION
vi docker-compose.yaml
docker-compose up

And send ~/byzcoin/public.toml to [email protected]

To setup a new node, you'll need to do the following steps:

1. Configure your node
2. Starting your node
3. Sign up for the DEDIS network
4. Updating your node

The simplest way of making your local configuration is to use the docker-compose file found in the root-directory of the byzcoin repository. In it you find the following variables:

# ADDRESS_NODE should always be tls:// - tcp:// is insecure and should
# not be used.
- ADDRESS_NODE=tls://byzcoin.c4dt.org:7770
# ADDRESS_WS can be either http:// or https:// - for most of the use-cases
# you want this to be https://, so that secure webpages can access the node.
- ADDRESS_WS=https://byzcoin.c4dt.org:7771
# A short description of your node that will be visible to the outside.
- DESCRIPTION="New ByzCoin node"
# Only needed if ADDRESS_WS is https. Ignored if it is http. 
- WS_SSL_CHAIN=fullchain.pem
- WS_SSL_KEY=privkey.pem
# ID of the byzcoin to follow - this corresponds to the DEDIS byzcoin.
- BYZCOIN_ID=9cc36071ccb902a1de7e0d21a2c176d73894b1cf88ae4cc2ba4c95cd76f474f3

The following variables are OK as default and can be changed if needed:

# How much debugging output - 0 is none, 1 is important ones, 2 is 
# interesting, 3 is detailed, 4 is lots of details, and 5 is too detailed for
# most purposes.
- DEBUG_LVL=2
# Whether to niceify the debug outputs. If you put this to `true`, you should
# have a black background in the terminal.
- DEBUG_COLOR=false
# Send tracing information to honeycomb.io. The format is: api_key:dataset.
# If no key is set, tracing is disabled.
- HONEYCOMB_API_KEY=

Update it with the address of your node, and eventually copy the SSL-files to the ~/byzcoin directory. The example for the ssl-files is given for letsencrypt files.

If you're running your node for the DEDIS 9cc3, please get in contact with [email protected], so that he can send you his HONEYCOMB_API_KEY. Then it'll be easier to trace eventual errors in the network.

Starting the node for the first time is done like this:

docker-compose up

This starts the node and prints some debugging information. If something goes wrong, an error is printed. Once the node is up and running, you can check it with:

go build go.dedis.ch/cothority/v3/status
status --host http://localhost:7771

Once it's running, start it in the background with:

docker-compose up -d

To get your node included in the DEDIS network, you need to sign the DEDIS_BYZCOIN.md file and send it, together with ~/byzcoin/public.toml to [email protected].

The docker-compose.yaml file contains a link to watchtower which will check every hour if there is a new docker-file available.

The current docker-compose.yaml contains a link to byzcoin:latest which is updated every day. To not have all the nodes update within one hour, it is better to link to one of the weekly snapshots: byzcoin:Sun, byzcoin:Mon, byzcoin:Tue, ..., byzcoin:Sat. By chosing a random day, the rebooting will be randomized over the week.

Once your node is up and running, you can get it started automatically from your crontab. Add the following line:

@reboot docker-compose restart

If you're running a node with its own private.toml and xxxxxx.db, the easiest way is to copy those two files in a ~/byzcoin directory and then adjust the following variables in docker-compose.yaml:

• ADDRESS_NODE=tls://byzcoin.c4dt.org:7770 # Change with your main address:port of the node
• ADDRESS_WS=http://byzcoin.c4dt.org # This is how your node will listen to websocket requests
• USE_TLS=false # Set this to 'true' if the node should handle TLS connections

This is taken from the point of view of the node. We suppose you have TLS some where:

1. The node is behind a proxy that handles TLS (apache, nginx, traefik, sstunnel, ...). url:port is where the proxy forwards the requests to the node. If you leave the ADDRESS_WS empty, it will take the default value, which is the same as ADDRESS_NODE, but using the next port.

  ADDRESS_WS=[https://url:port]

2. The node handles the certificates on its own. If you omit port, it defaults to 443:

  ADDRESS_WS=https://url[:port]
  USE_TLS=true

The public.toml file is re-generated according to the private.toml file. This brings some problems to the ADDRESS_WS, which is used for the URL parameter in the public.toml. If you have a proxy in front of the node, and the ADDRESS_WS is different from the proxy address, the URL parameter in public.toml will be wrong and you will have to adjust it manually.

In case the node handles its own certificates, and that you're using LetsEncrypt, you can create the following script:

cat <<EOF > /etc/letsencrypt/renewal-hooks/deploy/byzcoin.sh
#!/bin/bash
cp /etc/letsencrypt/live/url/{fullchain,privkey}.pem /home/conode/byzcoin
EOF
chmod a+x /etc/letsencrypt/renewal-hooks/deploy/byzcoin.sh

If you have a working dockerified trafik instance on your server, including a docker-wide network, you can add the following to your byzcoin service definition in docker-compose.yaml:

    environment:
      # ...
      - ADDRESS_WS=
      # ...
    labels:
     - "traefik.enable=true"
     - "traefik.http.routers.byzcoin.rule=Host(`byzcoin.c4dt.org`)"
     - "traefik.http.routers.byzcoin.entrypoints=websecure"
     - "traefik.http.routers.byzcoin.tls.certresolver=myresolver"
     - "traefik.http.services.byzcoin.loadbalancer.server.port=7771"
    networks:
     - traefik
     
networks:
  traefik:
    external:
      name: traefik_traefik # Adjust to match your traefik-installation

Before publishing your public.toml, you need to change the URL to:

URL = https://byzcoin.c4dt.org

Two github actions are used to update the code once per week and serve it over the coming week. The first action is started once a week to update the repo with the latest code from the cothority and onet to produce a docker file. The second action runs every day to update the link of the 'daily' docker image to the image from the first action.

Every node has currently a watchtower docker running once an hour and will update accordingly. As every node is linked to a different 'daily' docker image, the 7 nodes update throughout the week.

The following verifications are done before a new image is generated:

• a small unit-test for the binary
• the new code correctly replays all known transactions on the chain
• a cothority with 4 nodes can correctly migrate from the previous to the current nodes

All those tests are done in the update.yaml github action.

During heavy development, the automatic update is sometimes disabled. To update manually, use the following:

make update
git commit -am "updated to latest byzcoin"
git push

As this is still under development, sometimes it's nice to be able to update all nodes without having to wait for a week. This can be done using

make docker-push-all

This will create a new docker image and tag it for every weekday. As the current nodes update their image once an hour, you'll have to wait for an hour for every node to update. To mark these updates as somewhat not ideal, a force is added to the version.

The byzcoin binary has the following commands:

• config to set up a new config
• show to dump a config
• run to start the node as a server
• proxy to start a proxy

The config, show, and run commands are used in the docker and are not more explained here. Only the proxy command is interesting outside of docker.

You can run a proxy on your local computer for testing, e.g., if you're developing a new web-frontend. The proxy takes an existing db, like https://demo.c4dt.org/omniledger/cached.db, and serves it locally. When starting, the proxy does the following:

1. scan all chains in the db and update to the latest block
2. verify the stored state in the db and eventually updating it
3. regularly check for updates of the chain

The following arguments can be given to the proxy command:

• portWS for the websocket-port where the proxy will listen for commands
• update to change the intervals between two updates
• complete if given, the proxy makes sure all chains have all blocks available