You have been hired to provide advice about the use of cryptography to the developer of new two products within a company.

a. Group A is developing a product which will encrypt each user's data before storing it on the hard disk, and decrypt it as it is accessed. Confidentially should be preserved. They want to know what encryption algorithms to use, and how it should be used to achieve their goals. What advice would you give this group?

b. Group B is developing a product which will allow users to send encrypted messages to other users around the world. Users typically do not know each other directly, but they should be able to send messages for which integrity and confidentiality are preserved. They want to know what encryption algorithm(s) to use, and how it (they) should be used to achieve the goals. What advice would you give this group?