Term of the Moment
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Definition: challenge-response
An authentication method that proves the identity of users logging into a network. When a user logs in, the access server or authentication server sends a random number (the challenge) to the client. The client encrypts the password and challenge into a hash value that is sent to the server (the response). The server performs the same encryption and compares hashes. If they match, the user is verified.
Hardware Assisted
Challenge-response systems may also work with an authentication token, which is a smart card or credit-card sized card that users have in their possession. When they log in, they respond to the challenge by either inserting their smart card into a reader or typing in the password on the card's readout. See zero-knowledge proof, authentication token, authentication, access control and CHAP.
Challenge-Response Example
Hardware Assisted
Challenge-response systems may also work with an authentication token, which is a smart card or credit-card sized card that users have in their possession. When they log in, they respond to the challenge by either inserting their smart card into a reader or typing in the password on the card's readout. See zero-knowledge proof, authentication token, authentication, access control and CHAP.
In this example, either the network access server or the authentication server generates a random number and sends it to the client as the challenge. The client uses a hash algorithm to combine the challenge and password and send the result back. The originating component performs the same hash step and compares it to the client's results. If they match, the system knows the client has the correct password. See authentication server.