Whether you’re brand new to the Sia community or just need a refresher on the basics, this article will get you up to speed.

What is Sia

Sia is a decentralized cloud storage platform secured by blockchain technology. The Sia storage network leverages underutilized hard drive capacity around the world to create a data storage marketplace that is more reliable and lower cost than traditional cloud storage providers. Sia has its own blockchain, and a utility token that powers it – the Siacoin.

Your data is truly private and gets stored across the globe to eliminate any single point of failure and ensure the highest possible uptime. Since you hold the keys, you own your data. No outside company can access or control your files. Data cannot be de-platformed. Files can not be hacked.

Not only is your data safe on Sia, but you can feel confident that Sia isn’t going anywhere. Sia has been in development for six years and has been live for five. The Sia software has been downloaded over a million times, and thousands of TB have been uploaded to the network since its inception. If the Sia dev team quits tomorrow, the network can autonomously run forever.

Sia has an incredible ecosystem with renters, hosts, miners, and a teeming developer community building on Sia and the level 2 layer above Sia called Skynet.

How does Siacoin Work

Sia combines a peer-to-peer network with blockchain technology to create the world’s first decentralized storage platform. Here’s 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, which 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 storage proof. If the storage proof appears on the blockchain within a certain timeframe, the cost 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.

How Is the Siacoin Network Secured?

The Sia blockchain is secured using a proof-of-work consensus algorithm, meaning that miners compete with each other to add new blocks to the blockchain and a majority must confirm a record for it to be posted. Sia co-founder Vorick argued in June 2017 that proof-of-work is the best way to secure the network because it tethers a malicious actor’s ability to attack the network to massive energy requirements and hardware expenses.

According to Sia’s development team, the fact that hosts have to put up collateral in order to participate in the network’s operations decreases any incentive for bad actors. In addition, it has pointed to the fact that it splits uploaded data into 30 segments, which are then distributed across the globe, as reassurance that its network cannot be taken down except in the event of a massive natural disaster or geopolitical event. And as long as 10 out of 30 hosts survive an attack on its network, files can still be retrieved.