This interface represents an abstract challenge-response oriented authentication scheme.

An authentication scheme should be able to support the following functions:

• Parse and process the challenge sent by the targer server in response to request for a protected resource
• Provide its textual designation
• Provide its parameters, if available
• Provide the realm this authentication scheme is applicable to, if available
• Generate authorization string for the given set of credentials, request method and URI as specificed in the HTTP request line in response to the actual authorization challenge

Authentication schemes may ignore method name and URI parameters if they are not relevant for the given authentication mechanism

Authentication schemes may be stateful involving a series of challenge-response exchanges

[Android Documentation]