Simple CHT: A New Derivation of the Weakest Failure Detector for Consensus

The paper proposes an alternative proof that Ω, an oracle that outputs a process identifier and guaran-tees that eventually the same correct process identifier is output at all correct processes, provides minimal information about failures for solving consensus in read-write shared-memory systems: every oracle that gives enough failure information to solve consensus can be used to implement Ω. Unlike the original proof by Chandra, Hadzilacos and Toueg (CHT), the proof presented in this paper builds upon the very fact that 2-process wait-free consensus is impossible. Also, since the oracle that is used to implement Ω can solve consensus, the implementation is allowed to directly access consensus objects. As a result, the proposed proof is shorter and conceptually simpler than the original one.