Secure communication $(2$pt$.)$

Design a security service that provides data integrity, data confidentiality

and nonrepudiation using public$-$key cryptography in a two$-$party commu$-$

nication system over an insecure channel. Focus on the situation where

Alice and Bob want to exchange files in a secure way, with the properties

mentioned above. Use the cryptographic schemes and protocols seen in

the course.