The Blockstack Radiks feature enables Blockstack decentralized applications (DApps) to index and store across data belonging to multiple users. Radiks works with Blockstack's Gaia Storage System. Using Radiks, you can build multi-player DApps that:
Many applications serve data that users create to share publicly with others. Facebook, Twitter, and Instagram are examples of such applications. Decentralized applications that want to create comparable multi-user experiences must ensure that anything a user creates for public sharing is still under control of the creator in the user's Gaia storage.
For example, if Twitter wanted to be a decentralized application while still having many different users creating their own tweets, those tweets would be stored in each user's own Gaia storage. In such a situation, Twitter still needs a way to keep track of everyone's tweets, display those tweets in user timelines, and perform searches across the platform. Radiks exists to support these kinds of scenarios. It allows applications to query across multiple user data using complicated queries like text search, joins, and filters.
Radiks allows applications to query data in a performant and flexible way. Each application that wishes to index and query in this way requires its own Radiks server.
Radiks consists of a database, a pre-built server, and a client. A developer adds the Radiks library to their application. With this library, developers model their application data. The model defines an application data schema for the Radiks server. Then, you can use calls to write and query data that use that schema. Whenever an application saves or updates data on behalf of a user, Radiks follows this flow:
Radiks can store both public and sensitive, non-public data since all data is encrypted by default before it leaves the client. Your application can query Radiks for public data and then decrypt the sensitive information on the client. Radix servers can only return queries for unencrypted data.
Radiks must ensure that the user is writing to their own data. To ensure this, Radiks creates and manages *signing keys*. These keys sign all writes that a user performs. Radiks server-validates all signatures before performing a write. This guarantees that a user is not able to overwrite another user's data.
A Radiks server is also built to support writes in a collaborative but private situation. For example, consider a collaborative document editing application, where users can create organizations and invite users to that organization. All users in that organization should have read and write privileges to the organization data. Thus, these organizations will have a single shared key that is used to sign and encrypt data.
When an organization administrator needs to remove a user from the group, they are expected to revoke the previous key and create a new one. Radiks is aware of these relationships, and will only support writes that are signed with the currently active key related to an organization.
Although Radiks applications rely on a centrally-hosted database, an application using Radiks remains fundamentally decentralized. A DApp that uses Radiks has these characteristics.
<td><p>All user data is first stored in Gaia before encrypted with the user's keys and stored in Radiks. This process means the user still controls their data for as long as they need to. If the application's Radiks server shuts down, the user can still access their data. And, without the user's signing keys, an application cannot decrypt the user's data. Users may also backup or migrate their application data from Gaia.
<td><p>All data is encrypted on the client-side before being stored anywhere using Blockstack authorization. The application host cannot inspect, sell, or use user data in any way that a user doesn't explicitly authorize.
