The HTTP Proxy-Authorization request header contains the credentials to authenticate a user agent to a proxy server, usually after the server has responded with a 407Proxy Authentication Required status and the Proxy-Authenticate header.
The username and the password are combined with a colon (aladdin:opensesame).
The resulting string is base64 encoded (YWxhZGRpbjpvcGVuc2VzYW1l).
Note: Base64 encoding does not mean encryption or hashing! This method is as secure as sending the credentials in clear text (base64 is a reversible encoding). It is preferable to use HTTPS in conjunction with Basic Authentication.