A SIA file is a metadata file used by Sia, a decentralized cloud storage network that utilizes blockchain technology. It contains metadata about one or more files that have been uploaded to the Sia network, which includes an encryption key and the locations of the hosts that are storing the uploaded files.
SIA files allow users to share files that they have uploaded to the network with other users.
Sia was developed to compete against large cloud storage platforms, such as Google Drive, iCloud, and Dropbox, giving Sia users more affordable options for cloud storage. Users, or "renters," can purchase contracts with other users, or "hosts," for storage space on the Sia blockchain using Siacoin, a cryptocurrency similar to Bitcoin.
The renters then upload their files through Sia and the files are divided into 30 different segments. This method helps protects against data loss due to cyberattacks or downed servers by spreading the storage across different spaces. 10 of the 30 segments are required for Sia renters to retrieve stored data. The SIA file is used by Sia to verify that the user has permission to access the uploaded files.
NOTE: The first version of the SIA file format was released in May 2015 with multiple versions subsequently released.