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Casper CBC

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A python implementation of a class of "correct-by-construction" consensus protocols. Currently, this includes Casper the Friendly Ghost (a blockchain consensus protocol) and Casper the Friendly Binary Consensus Protocol.

Specifications for these protocols can be found here here, but the implementation and the spec may deviate from the spec, as they are still moving targets.

Warning -- Codebase subject to substantial changes

This pre v1.0 implementation is under active development and experimentation and might experience significant organizational and substantive changes. If you use components of this codebase, expect breaking changes to be introduced.

That said, we will try to detail any breaking changes in subsequent releases.


  • Python 3
  • ubuntu/debian: sudo apt-get install python3-dev python3-venv python3-tk
  • OSX via Homebrew: brew install python3

Developer Setup

If you would like to hack on cbc-casper or run the simulations yourself, setup your dev environment with:

make install

NOTE: If you prefer to manage venv explicitly, run a standard venv setup and pip install using requirements.txt

Run Simulations


Standard simulations are marked up for use as follows:

make run-[binary | blockchain | concurrent | integer | order | sharding]

Each protocol represents consensus on a different data structure.

Optionally, you can add a message passing mode to each protocol. For example,

make run-binary MODE=rrob

There are currently three message passing modes:

rand: each round, some randomly selected validators propagate their most recent message to other randomly selected validators, who then create new messages.

rrob: each round, the creator of the last round's block sends it to the next receiver, who then creates a block.

full: each round, all validators receive all other validators previous messages, and then all create messages.

By default, a gif and associated images of the simulation will be saved in graphs/graph_num_0/. These settings can be modified, along with the number of validators, the number of messages that propagate per round, and the report interval in the config.ini.


Advanced simulations can be run with a little command line wizardy.

  • First ensure that you are using the virtual environment via: . venv/bin/activate
  • Simulations can then be run via The following are example usages:
# get help and all options for
python --help

# run a simulation with 100 validators and random message propagation
python --protocol blockchain --msg-mode rand --validators 100

# run a simulation without displaying the viewgraphs, but instead save them and create a GIF
python --protocol blockchain --msg-mode rand --display false --save true

# run a simulation with 20 validators and 1000 rounds of round robin message propagation,
# reporting every 100 rounds
python --protocol blockchain --msg-mode rrob --validators 6 --rounds 300 --report-interval 100

Write Simulations


Run Tests

To run all tests:

make test

To run a specific test, use (or the equivalent for whatever test you wish to run)

make test TEST=tests/

To run tests with visualizations:

make test-with-reports

Note: each view graph must be closed for the tests to continue running.