Traditional web federation does not describe how a client interacts with an IdP for authentication. As a result, this communication is not standardized. There are several disadvantages to this approach. Since the communication is not standardized, it is difficult for machines to recognize which entity is going to do the authentication, and thus which credentials to use and where in the authentication form the credentials are to be entered. It is much easier for humans to correctly deal with these problems. The use of browsers for authentication restricts the deployment of more secure forms of authentication beyond plaintext usernames and passwords known by the server. In a number of cases, the authentication interface may be presented before the client has adequately validated that they are talking to the intended server. By giving control of the authentication interface to a potential attacker, the security of the system may be reduced, and opportunities for phishing may be introduced.