Sia is a decentralized cloud storage platform similar in concept to Dropbox and other centralized storage provider where instead of renting storage space from a centralized entity, clients rent storage space from other peers. The only difference is Sia uses blockchain to facilitate transactions. Nodes provide storage to clients using the Sia blockchain as contracts. Before storing the data, the data is encrypted into many pieces and uploaded to different hosts.
Siacoin was created by David Vorick and Luke Champine of Nebulous Inc. Siacoin promises to offer secured storage transactions with smart contracts which is more affordable and reliable. Moreover, it is completely open source which means many individuals have contributed to Siacoin’s software and building applications on top of the Sia API.