Consider the following scenarios. Find a total of four vulnerabilities in the following scenarios, and, for each vulnerability, indicate which security goal (confidentiality, integrity, or availability) is threatened, with a one sentence justification of how. Propose an approach that mitigates the vulnerability that you describe. Note that you should find at least one vulnerability per scenario.

A PHP program stores a user's login name and password in a cookie on the user's machine for a limited amount of time. In order to prevent an unauthorized individual from recovering these credentials, the cookie is encrypted using the DES algorithm with a 56-bit key that is securely stored on the server.

Bob has written an implementation of AES-256/ECB which he plans to use to encrypt the contents of back up tapes that are sent to an offsite storage facility.

Alice is taking a different approach. She has designed her own symmetric key encryption program, and she would like to use this instead of Bobs. She believes that this approach will lead to a more secure approach since both the key and the encryption algorithm will be secret.