Proof of space

Proof of space is a consensus technique in which a participant shows that it has set aside a non-trivial amount of memory or disk space, instead of burning computation as in proof of work. A prover sends the verifier a piece of data demonstrating that the space is reserved, and the check is meant to be cheap in both time and space while remaining hard to pass without really holding the storage. One construction asks the prover to build and commit to a labeling of a hard-to-pebble graph, after which the verifier asks it to open several random positions of the commitment. The idea was formulated in 2013 by Dziembowski and colleagues and, with a different formulation, by Ateniese and colleagues, and it grew out of the search for alternatives to Bitcoin mining that waste less energy. Related ideas include proof of storage, proof of capacity and proof of space-time. Signum, formerly Burstcoin, was the first practical implementation in 2014, followed by designs such as SpaceMint and Chia.