Posts Tagged ‘login protocol

User login protocol

Initialization: Once the user has successfully logged into an account, the server places in the user’s computer a cookie that contains an authenticated record of the username, and possibly an expiration date. (“Authenticated”means that no party except for the server is able to change the cookie data without being detected by the server. This can be ensured, for example, by adding a MAC that is computed using a key known only to the server. Cookies of this type can be stored in several computers, as long as each of them was used by the user.


1. The user enters a username and a password. If his computer contains a cookie stored by the login server then the cookie is retrieved by the server.

2. The server checks whether the username is valid and whether the password is correct for this username.

3. If the username/password pair is correct, then

4. If the username/password pair is incorrect, then

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