Blockchain-based marketplace for file storage

2 years after

Sia Logo v1.1.2 (Andromeda)


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Sia is a new decentralized cloud storage platform that radically alters the landscape of cloud storage. By leveraging smart contracts, client-side encryption, and sophisticated redundancy (via Reed-Solomon codes), Sia allows users to safely store their data with hosts that they do not know or trust. The result is a cloud storage marketplace where hosts compete to offer the best service at the lowest price. And since there is no barrier to entry for hosts, anyone with spare storage capacity can join the network and start making money.


Traditional cloud storage has a number of shortcomings. Users are limited to a few big-name offerings: Google, Microsoft, Amazon. These companies have little incentive to encrypt your data or make it easy to switch services later. Their code is closed-source, and they can lock you out of your account at any time.

We believe that users should own their data. Sia achieves this by replacing the traditional monolithic cloud storage provider with a blockchain and a swarm of hosts, each of which stores an encrypted fragment of your data. Since the fragments are redundant, no single host can hold your data hostage: if they jack up their price or go offline, you can simply download from a different host. In other words, trust is removed from the equation, and switching to a different host is painless. Stripped of these unfair advantages, hosts must compete solely on the quality and price of the storage they provide.

Sia can serve as a replacement for personal backups, bulk archiving, content distribution, and more. For developers, Sia is a low-cost alternative to Amazon S3. Storage on Sia is a full order of magnitude cheaper than on S3, with comparable bandwidth, latency, and durability. Sia works best for static content, especially media like videos, music, and photos.

Distributing data across many hosts automatically confers several advantages. The most obvious is that, just like BitTorrent, uploads and downloads are highly parallel. Given enough hosts, Sia can saturate your bandwidth. Another advantage is that your data is spread across a wide geographic area, reducing latency and safeguarding your data against a range of attacks.

It is important to note that users have full control over which hosts they use. You can tailor your host set for minimum latency, lowest price, widest geographic coverage, or even a strict whitelist of IP addresses or public keys.

At the core of Sia is a blockchain that closely resembles Bitcoin. Transactions are conducted in Siacoin, a cryptocurrency. The blockchain is what allows Sia to enforce its smart contracts without relying on centralized authority. To acquire siacoins, use an exchange such as Poloniex, Yunbi, or Bitsquare.

To get started with Sia, check out the guides below:


Sia is ready for use with small sums of money and non-critical files, but until the network has a more proven track record, we advise against using it as a sole means of storing important data.

This release comes with 2 binaries, siad and siac. siad is a background service, or "daemon," that runs the Sia protocol and exposes an HTTP API on port 9980. siac is a command-line client that can be used to interact with siad in a user-friendly way. There is also a graphical client, Sia-UI, which is the preferred way of using Sia for most users. For interested developers, the siad API is documented here.

siad and siac are run via command prompt. On Windows, you can just double- click siad.exe if you don't need to specify any command-line arguments. Otherwise, navigate to its containing folder and click File->Open command prompt. Then, start the siad service by entering siad and pressing Enter. The command prompt may appear to freeze; this means siad is waiting for requests. Windows users may see a warning from the Windows Firewall; be sure to check both boxes ("Private networks" and "Public networks") and click "Allow access." You can now run siac (in a separate command prompt) or Sia- UI to interact with siad. From here, you can send money, upload and download files, and advertise yourself as a host.

Building From Source

To build from source, Go 1.7 must be installed on the system. Then simply use go get:

go get -u

This will download the Sia repo to your $GOPATH/src folder, and install the siad and siac binaries in your $GOPATH/bin folder.

To stay up-to-date, run the previous go get command again. Alternatively, you can use the Makefile provided in this repo. Run git pull origin master to pull the latest changes, and make release-std to build the new binaries. You can also run make test and make test-long to run the short and full test suites, respectively. Finally, make cover will generate code coverage reports for each package; they are stored in the cover folder and can be viewed in your browser.

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