Sia is reinventing cloud storage. Our technology connects users who need file storage with hosts worldwide offering underutilized hard drive capacity. Blockchain technology secures their data and enables improved economics for users and hosts.
The Sia blockchain allows this marketplace to run without an intermediary. Sia secures storage transactions with smart contracts, creating a more reliable and affordable offering when compared to traditional cloud providers.
No one, person or organization, can censor or deny access to data — not miners, not developers, nor any government.

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How Sia Works?

• Files Are Divided Prior To Upload
  The Sia software divides files into 30 segments before uploading, each targeted for distribution to hosts across the world. This distribution assures that no one host represents a single point of failure and reinforces overall network uptime and redundancy.
  File segments are created using a technology called Reed-Solomon erasure coding, commonly used in CDs and DVDs. Erasure coding allows Sia to divide files in a redundant manner, where any 10 of 30 segments can fully recover a user's files.
  This means that if 20 out of 30 hosts go offline, a Sia user is still able to download her files.
• Each File Segment Is Encrypted
  Before leaving a renter's computer, each file segment is encrypted. This ensures that hosts only store encrypted segments of user data.
  This differs from traditional cloud storage providers like Amazon, who do not encrypt user data by default. Sia is more secure than existing solutions because hosts only store encrypted file segments, rather than whole files.
  Sia uses the Threefish algorithm, an open source, secure, high-performance encryption standard.
• Files Are Sent To Hosts Using Smart Contracts
  Using the Sia blockchain, renters form file contracts with hosts. These contracts set pricing, uptime commitments, and other aspects of the relationship between the renters and the hosts.
  File contracts are a type of smart contract. They allow us to create cryptographic service level agreements (SLAs) that are stored on the Sia blockchain.
  Since file contracts are automatically enforced by the network, Sia has no need for intermediaries or trusted third parties.
• Renters And Hosts Pay With Siacoin
  Both renters and hosts use Siacoin, a unique cryptocurrency built on the Sia blockchain. Renters use Siacoin to buy storage capacity from hosts, while hosts deposit Siacoin into each file contract as collateral.
  Micropayments flow between renters and hosts using a technology called payment channels, which is similar to Bitcoin's Lightning Network. Payments between renters and hosts occur off-chain, greatly increasing network efficiency and scalability.
  Since hosts pay collateral into every storage contract, they have a strong disincentive to go offline.
• Contracts Renew Over Time
  Renters prepay for storage within file contracts, setting aside a fixed amount of Siacoin to be spent on storing and transferring data. File contracts typically last 90 days.
  Sia automatically renews contracts when they are within a certain window of expiring. If contracts are not renewed, Sia returns any unused coins to the renter at the end of the contract period.
  As individual hosts go offline, Sia automatically moves renter data to new hosts in a process called file repair.
• Hosts Submit Storage Proofs
  At the end of a file contract, the host must prove that she is storing the renter's data. This is called a storage proof. If the storage proof appears on the blockchain within a certain timeframe, the host is paid. If not, the host is penalized.
  Storage proofs are made possible by a technology called Merkle trees. Merkle trees make it possible to prove that a small segment of data is part of a larger file. The advantage of these proofs is that they are very small, no matter how large the file is. This is important because the proofs are stored permanently on the blockchain.

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What are Siacoins?

Siacoins are the utility tokens that power the Sia network. They allow you to upload files to Sia, a decentralized cloud network powered by blockchain technology.
Siacoins are used in lots of ways, but serve a single purpose – facilitating network operations. When you upload files to Sia, you pay for that storage in Siacoins. If you're a host and you're storing other people's data, you get paid for that in Siacoins. If you own Siafunds, your share of Sia network growth is paid out in, you guessed it, Siacoins.
You can send Siacoins to others, or receive them at your own wallet address. You can store them in our official software, or on a hardware or paper wallet. You can get Siacoins by having someone send them to you, buying them on an exchange, or mining them.
New Siacoins are only made by mining. There's over 40 billion Siacoins out there right now, and that number will never stop growing. Sia is going to be the storage layer of the internet, and billions will be required for the petabytes and exabytes of data that will be stored on Sia.