Equivalency of agreement problems Consensus (computer science)

1 equivalency of agreement problems

1.1 terminating reliable broadcast
1.2 consensus
1.3 weak interactive consistency

equivalency of agreement problems

three agreement problems of interest follows.

terminating reliable broadcast

a collection of n processes, numbered 0 n - 1, communicate sending messages 1 another. process 0 must transmit value v processes such that:

it known general s problem.

consensus

formal requirements consensus protocol may include:

agreement: correct processes must agree on same value.
weak validity: if correct processes receive same input value, must output value.
strong validity: each correct process, output must input of correct process.
termination: processes must decide on output value

weak interactive consistency

for n processes in partially synchronous system (the system alternates between , bad periods of synchrony), each process chooses private value. processes communicate each other rounds determine public value , generate consensus vector following requirements:

it can shown variations of these problems equivalent in solution problem in 1 type of model may solution problem in type of model. example, solution weak byzantine general problem in synchronous authenticated message passing model leads solution weak interactive consistency. interactive consistency algorithm can solve consensus problem having each process choose majority value in consensus vector consensus value.