A proof-of-replication (PoRep) is a proof system that a server can use to demonstrate to a network in a publicly verifiable way that it is dedicating unique resources to storing one or more replicas of a data file. While it is not possible for PoReps to guarantee cryptographically that the prover's storage format is redundant, PoReps do guarantee that: (a) The prover must be using as much space to produce the proof as replicas it claims to store (it is a proof of space) (b) The prover can retrieve a committed data file (it is a proof of retrievability) (c) The prover can use the space to store this file without any overhead In this sense a PoRep is a useful proof of space. It is uniquely suited to replace proof-of-work in Nakamoto consensus as a Sybil resistance mechanism, while simultaneously incen-tivizing and subsidizing the cost of file storage. Technical report This is a short technical report on our constructions. A more detailed paper is forthcoming with information about our prototype implementation of PoReps.