### 2023-08-30/Report

## Filecoin Proof of Useful Space

[Irene Giacomelli](https://research.protocol.ai/authors/irene-giacomelli/), [Luca Nizzardo](https://research.protocol.ai/authors/luca-nizzardo/)

[Cryptonet](https://research.protocol.ai/groups/cryptonet/)

[Cryptography](https://research.protocol.ai/areas/cryptography/)

## Abstract

This document provides a simple formal definition of Proof of Space (taken from the academic literature) and an informal definition of persistent and useful space (needed for Filecoin). It describes construction details and a security proof for the Stacked-DRGs proof of space (SDR), and goes into how SDR is used in Filecoin. In particular, it includes a description and analysis for Filecoin’s PoRep, WindowPoSt and WinningPoSt.

### Resources

[Download PDF](https://research.protocol.ai/publications/filecoin-proof-of-useful-space/giacomelli2023.pdf)