A challenge/response system is a technique where it can overcomes the problem of attacker eavesdropping by initiating a dialog between the host and the user. The information exchanged as part of the dialog depends upon some secret information held by the host and user, but this secret information is never transmitted. In this system, identification is by the user-ID. Each user is issued an intelligent token. Not only that, they will also be assigned …showed first 75 words of 368 total…

…showed last 75 words of 368 total…computes: (26 + 35) x 11 = 671 and returns the response 671. The host obtains +, 35 and x from the login file entry corresponding to the user ID, performs the corresponding calculation on the challenge, and compares the result with the user response. If the response is incorrect, the host may allow additional login attempts but changes the challenge on each occasion. So, this is basically what the "challenge/response" system is and to show it more clearly, refer to the Figure 1.