and O (to indicate the user was not subscribed) were added. With the exception of Official MSN Staff. It was impossible for a user with the mode "O" to chat in a channel with the Channel Mode "S". Update to the GateKeeper Authentication method (known as the "4.5 Auth", due to the MSN Chat Control 4.5 being the first to implement it). It was a slight change, that added the value taken from the Server Parameter (before the ":" (if one is present)) to a MD5 Checksum. Third-party applications The use of third-party applications on the MSN Chat Network was not prohibited, although it was unsupported. Third-party applications were required to use the same Authentication Methods as the MSN Chat Control. The second change was the major part, allowing the Chat Control to bridge the connections between the Client and MSN Chat Service. The most popular third-party applications were mIRC, IRC Dominator and Viperbot. Scripts were often downloaded from sites such as TechGear007. Notable features Webchat using MSN's Chat Control Chat nicknames Profiles Chatroom creation Emoticons Chatroom listings User created rooms MSN created rooms MSN WebTV chats Celebrity chats Adult chats, moderate content chats, all aged chats Integration with MSN groups Authentication GateKeeper The GateKeeper (and closely related GateKeeperPassport) authentication mechanisms are SASL authentication mechanisms as defined in the IRCX Drafts. After the introduction of authentication on MSN Chat, Gatekeeper was the only authentication method that the public could use. During the initial handshake, the client would send a packet only containing the 16 byte header to the server, and the server would reply with a header, coupled with a 128 bit Cryptographic nonce. Finally, the client would create a 128 bit cryptographic hash of the nonce received from the server using a secret key, sending this as a subsequent authentication reply after the header, and immediately before a 16 byte GUID. The cryptographic hash function used was hmac-md5, and the secret key was "SRFMKSJANDRESKKC" (case sensitive). Defeating GateKeeper Early implementations of the GateKeeper authentication mechanism did not create a barrier to entry, as the authentication API that Microsoft had created was available to other program developers. After some time, Microsoft removed the ability for developers to use/see the API that had been embedded in the MSN Chat Control, and it can be safely assumed from this time that Microsoft wanted access to be from the official chat control only.