Patent ID: 7395311

Claim:
In a distributed system including a server message processor that is communicatively coupled to one or more other message processors such that the server message processor and the one or more other message processors can communicate by transferring electronic messages, a method for the server message processor to challenge a client message processor, the method comprising: an act of receiving a first electronic request from the client message processor to access a service at the server message processor; an act of identifying a type of challenge from among a plurality of different types of challenges, each different type of challenge having corresponding different algorithmic processing utilized for computing a response to the type of challenge; an act of issuing a challenge along with a token to the client message processor, the challenge and token issued in accordance with the identified type of challenge, the token containing state information related to the challenge such that the server message processor is relieved from having to use system resources to maintain state information related to the challenge while waiting for a response to the challenge; an act of receiving a second electronic request to access the service from the client message processor, the second electronic request including a response to the challenge and the token, the response containing an answer to the challenge; and an act of comparing the contained answer to the state information contained in the token to determine if the answer represents an appropriate answer to the challenge without referring to other maintained state information related to the challenge.