Flexible byzantine fault tolerance

A system configured to perform a flexible byzantine fault tolerant (BFT) protocol for a consensus, the system comprising:

• a client device comprising:
• a transceiver configured to transmit and receive signals, and
• a processor configured to control the transceiver to send, to a plurality of replica devices, a proposed value,
• the plurality of replica devices, each of the plurality of replica devices comprising:
• a transceiver configured to receive the proposed value from the client device, and
• a processor configured to determine to send a safe vote based on a first quorum threshold being reached,
• wherein the transceiver of the plurality of replica device is further configured to transmit the safe vote to the client device and each of the other plurality of replica devices,
• wherein the processor of the client device is further configured to:
• determine that a number of received safe votes, received from at least one of the replica devices, for the proposed value meets or exceeds a second quorum threshold,
• select the proposed value based on the determination,
• set a period of time within which to receive additional votes from at least one of the plurality of replica devices, wherein the period of time is a network delay bound for a single view of the BFT protocol, and
• based on the period of time elapsing without receiving the additional votes, commit the selected value for the single view of the BFT protocol.

A non-transitory computer storage medium storing instructions executable by a first computer system at a first site that, when executed by a processor of the first computer system, cause the processor to:

• send, from a client device, a proposed value to a plurality of replica devices;
• receive, from at least one of the plurality of replica devices, a safe vote on the proposed value, wherein the at least one of the plurality of replica devices determines to send the safe vote based on a first quorum being reached and the safe vote is sent to the client device and each of the other replica devices of the plurality of replica devices;
• determine that a number of received safe votes, received from the at least one of the replica devices, for the proposed value meets or exceeds a second quorum threshold;
• select the proposed value based on the determination;
• set a period of time within which to receive additional votes from at least one of the plurality of replica devices, wherein the period of time is a network delay bound for a single view of a BFT protocol;
• and
• based on the period of time elapsing without receiving the additional votes, commit the selected value for the single view of the BFT protocol.