Fast Practical Byzantine Fault Tolerance is trickier than you might think

Over a decade of improvements to the seminal PBFT work have turned out to have safety or liveness issues, as demonstrated in a recent ArXiv note we posted:

• Revisiting Fast Practical Byzantine Fault Tolerance.
  Ittai Abraham, Guy Gueta, Dahlia Malkhi; with Lorenzo Alvisi, Rama Kotla, Jean-Philippe Martin. [ArXiv 2017] [pdf]