PoST (Proof of Space Time) is a sub-protocol of NiPoST. It is the algorithm that proves that the committed disk space was used for the Spacemesh protocol. The algorithm first generates unique data that occupies that committed disk space. Once this initialization phase is completed, each execution of the PoST algorithm provides a proof for the existence of the data (that the data was not erased). The Smesher executes PoST after each full execution of the PoET algorithm.