How to get user name from http header?

I am trying to get the user login from the http header. I have tried@GetHTTPHeader(“Authorization”) but it returned " Authorization: Basic

Z2FuZGFsZjp0aGUtd2l6YXJk ". Any functions that would decrypt it.

Thanks.

Subject: Wrong Header-Field

Try @GetHTTPHeader(“REMOTE_USER”)

SG Michael Tassati