Welcome to the resource topic for
**2018/702**

**Title:**

Tight Proofs of Space and Replication

**Authors:**
Ben Fisch

**Abstract:**

We construct a concretely practical proof-of-space (PoS) with arbitrarily tight security based on stacked depth robust graphs and constant-degree expander graphs. A proof-of-space (PoS) is an interactive proof system where a prover demonstrates that it is persistently using space to store information. A PoS is arbitrarily tight if the honest prover uses exactly N space and for any \epsilon > 0 the construction can be tuned such that no adversary can pass verification using less than 1-\epsilon N space. Most notably, the degree of the graphs in our construction are independent of \epsilon, and the number of layers is only O(\log(1/\epsilon)). The proof size is O(d/\epsilon). The degree d depends on the depth robust graphs, which are only required to maintain \Omega(N) depth in subgraphs on 80% of the nodes. Our tight PoS is also secure against parallel attacks. Tight proofs of space are necessary for proof-of-replication (PoRep), which is a publicly verifiable proof that the prover is dedicating unique resources to storing one or more retrievable replicas of a file. Our main PoS construction can be used as a PoRep, but data extraction is as inefficient as replica generation. We present a second variant of our construction called ZigZag PoRep that has fast/parallelizable data extraction compared to replica generation and maintains the same space tightness while only increasing the number of levels by roughly a factor two.

**ePrint:**
https://eprint.iacr.org/2018/702

**Talk: **https://www.youtube.com/watch?v=84kHVqvTVcw

See all topics related to this paper.

Feel free to post resources that are related to this paper below.

**Example resources include:**
implementations, explanation materials, talks, slides, links to previous discussions on other websites.

For more information, see the rules for Resource Topics .