  This paper describes a simple and efficient Binary Byzantine faulty tolerant
consensus algorithm using a weak round coordinator and the partial synchrony
assumption to ensure liveness. In the algorithm, non-faulty nodes perform an
initial broadcast followed by a executing a series of rounds consisting of a
single message broadcast until termination. Each message is accompanied by a
cryptographic proof of its validity. In odd rounds the binary value 1 can be
decided, in even round 0. Up to one third of the nodes can be faulty and
termination is ensured within a number of round of a constant factor of the
number of faults. Experiments show termination can be reached in less than 200
milliseconds with 300 Amazon EC2 instances spread across 5 continents even with
partial initial disagreement.
