TIdBasicAuthentication = class(TIdAuthentication);

TIdBasicAuthentication is a TIdAuthentication descendant that implements the Basic Authentication mechanism described in the Internet Standards documents: 

RFC 2616 - Hypertext Transfer Protocol [HTTP/1.1]  

RFC 2617 - HTTP Authentication: Basic and Digest Access Authentication  

TIdBasicAuthentication provides properties and methods needed to process user authentication in TIdHTTP client for HTTP requests and response using the "Basic" Authentication scheme. TIdBasicAuthentication implements support for client authentication using Username and Password values for the Realm specified in the WWW-Authenticate header of an HTTP server or proxy response. 

TIdBasicAuthentication allows the client to construct the base64-encoded client credentials needed in the response to a server or proxy authentication challenge. The Authentication value is used in the HTTP Authorization header expressed in the following form: 

  Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

TIdBasicAuthentication is the default authentication scheme registered for use with the TIdHTTP client using the RegisterAuthenticationMethod procedure. 

Use TIdDigestAuthentication to implement support for the Digest Access Authentication Scheme in TIdHTTP client by calling the RegisterAuthenticationMethod procedure with the appropriate arguments.