Leslie Lamport describes a secure password authentication method that protects against intruders who can read system data or eavesdrop on communication between a user and a system. The method uses a one-way encryption function and can be implemented on a microcomputer. The system stores a transformed version of the user's password, not the password itself. When a user logs in, they send their password to the system, which checks if the transformed password matches the stored value. This method prevents intruders from learning the password directly, as it is infeasible to reverse the one-way function. To prevent eavesdropping, the method uses a sequence of passwords. The system stores transformed values of these passwords, ensuring they are distinct. The user's password sequence is determined in advance, making it impossible for an intruder to impersonate the user even if they intercept the communication. The method also includes a robustness feature that allows the system to detect and correct synchronization issues between the user and the system. The method is secure against tampering and eavesdropping. Even if an intruder intercepts the communication, they cannot determine the user's password because the one-way function is infeasible to reverse. The system can also recover from crashes by jumping forward in the password sequence rather than backing up to a previously used password. The method is implemented using a microcomputer in the user's terminal. The user randomly selects a value, computes a sequence of transformed values, and sends the final value to the system. The system uses this value to authenticate subsequent passwords. The method is robust and can be used with removable storage devices for different systems. Needham and Schroeder's signature authentication protocol is shown to fail when keys are compromised. A more reliable method is proposed that requires a third party to verify the authenticity of the message, ensuring a stronger authentication mechanism.Leslie Lamport describes a secure password authentication method that protects against intruders who can read system data or eavesdrop on communication between a user and a system. The method uses a one-way encryption function and can be implemented on a microcomputer. The system stores a transformed version of the user's password, not the password itself. When a user logs in, they send their password to the system, which checks if the transformed password matches the stored value. This method prevents intruders from learning the password directly, as it is infeasible to reverse the one-way function. To prevent eavesdropping, the method uses a sequence of passwords. The system stores transformed values of these passwords, ensuring they are distinct. The user's password sequence is determined in advance, making it impossible for an intruder to impersonate the user even if they intercept the communication. The method also includes a robustness feature that allows the system to detect and correct synchronization issues between the user and the system. The method is secure against tampering and eavesdropping. Even if an intruder intercepts the communication, they cannot determine the user's password because the one-way function is infeasible to reverse. The system can also recover from crashes by jumping forward in the password sequence rather than backing up to a previously used password. The method is implemented using a microcomputer in the user's terminal. The user randomly selects a value, computes a sequence of transformed values, and sends the final value to the system. The system uses this value to authenticate subsequent passwords. The method is robust and can be used with removable storage devices for different systems. Needham and Schroeder's signature authentication protocol is shown to fail when keys are compromised. A more reliable method is proposed that requires a third party to verify the authenticity of the message, ensuring a stronger authentication mechanism.