Blockstack authentication is a bearer token-based authentication system. From an app user's perspective, login similar to third-party authentication techniques that they're familiar with. For an app developer, the flow is unlike the typical client-server flow of centralized sign-in services such as OAuth. With Blockstack the authentication flow happens entirely client-side.
In this section, you get an overview of the authentication system and learn how Gaia fits into it.
When a user chooses to "Sign in with Blockstack" on your DApp, the `redirectToSignIn()` method sends the user to the Blockstack authenticator. The browser responds with an authentication token and an _app private key_.
The app private key is application-specific. It is generated from the user's identity address private key using the `appDomain` as input. This key is deterministic, meaning that for a given Blockstack ID and domain name, the same private key is generated each time. The app private key is securely shared with the app on each authentication and encrypted by the Blockstack authenticator. The key serves three functions, it:
