Proof of Replication

We introduce Proof-of-Replication (PoRep), a new kind of Proof-of-Storage, that can be used to prove that some data D has been replicated to its own uniquely dedicated physical storage. Enforcing unique physical copies enables a verifier to check that a prover is not deduplicating multiple copies of D into the same storage space. This construction is particularly useful in Cloud Computing and Decentralized Storage Networks, which must be transparently verifiable, resistant to Sybil attacks, and unfriendly to outsourcing. This work (a) reviews Proofs-of-Storage and motivates use cases; (b) defines the novel Proofs-of-Replication, which can be publicly verifiable, transparent, authenticated, and time-bounded ; (c) shows how to chain Proofs-of-Replication to establish useful Proofs-of-Spacetime. Work in Progress. This is a work in progress Technical Report from Protocol Labs. Active research is under way, and new versions of this paper will appear. For comments and suggestions, contact us at [email protected] 1 Motivation and Background on Proofs-of-Storage This section provides backgrounds and classifications of different Proofs-of-Storage and related proofs, and motivates the need for Proofs-of-Replication. Throughout this section, we explain the distinction between different proofs using a prover, P, that is attempting to convince a verifier, V, that P is storing some data, D. V issues a challenge, c, to P who answers it with a corresponding proof π, according to the scheme in question. Proof schemes vary in their properties, their utility, and in whether D is useful outside the protocol or is a random string with no external utility. 1.1 Common Properties We use the following properties, common to various proving schemes: • (Privately Verifiable) A scheme is privately verifiable if V is a user with a secret verifying key generated during setup, or any other party that shares such secret key with the user. These schemes are useful in Cloud Computing settings, where users wish to outsource storage of data to servers and perhaps outsource verifying to a trusted verifier. As of this work, most Proof-of-Storage (PoS) schemes are privately verifiable. • (Publicly Verifiable) A scheme is publicly verifiable if V can be any party with access to public data (e.g. a verifying key), but no access to the original data, or secret information generated during scheme setup. Publicly verifiable schemes are very useful in Decentralized Storage Network settings, where a verifier may be new participants who have access only to public data as context of previous proof scheme setups. • (Transparent) A scheme is transparent if there is no extra information, sk, that enables any P to generate a valid proof without having data, D. This means that there is no sk with which a malicious prover can generate proof π∗ = ForgeProof(c, sk) such that 1 = Verify(c, π∗) for a P-chosen c. Transparent schemes