Sia is a network of decentralized storage created by Nebulous Labs. Using a peer-to-peer decentralized network, it creates a marketplace of cloud storage where some users act as hosts that offer free space in their disks and other users act as renters that pay for using that storage space.

According to its creators, the ultimate goal of Sia is becoming the backbone storage layer of the Internet. Anyone can rent his unused hard disk space, thus creating a network of decentralized datacenters.

Sia software is licensed under the MIT license and its code is open source, meaning that independent developers can contribute to the software and build new applications on top of it.

• Siacoin is the instrument for paying the file contracts. They can be acquired by mining or in exchanges
• Siafund is the asset created for fundraising the project and maintain the developing team. Owners receive a proportion of the 3.9% of fees charged on every file contract.

Sia uses its own blockchain to store all token transactions, file contracts, the database of hosts and the proofs of storage hosts have to fulfill to demonstrate they are actually hosting the files. The blockchain also enforces the payments associated to the file contracts.

The blockchain is secured by the Proof of Work algorithm Blake2b, being miners rewarded with newly issued Siacoins. The reward will decrease over time until it reaches 30000 Siacoin per block. This means the inflation is reducing over time in a predictable fashion.

• Decentralized: While Nebulous Labs develop the software, the network is decentralized, meaning that no central authority governs transactions, file contracts management or coin issuance.
• Encrypted: Files stored in Sia are encrypted using the Twofish cryptographic algorithm, and only the renter owns the decryption keys.
• Redundant: Files are stored across multiple hosts using Reed-Solomon redundancy algorithm, ensuring that even if multiple hosts go offline, the renter will still have access to his files.
• Affordable: Being a competitive marketplace, average storage prices are much lower than usual cloud storage providers, even considering the redundancy.