To secure network communications over public networks such as the Internet, it is necessary to build security network protocols. Network security protocols are applications of cryptographic algorithms, referred to as cryptographic building blocks, which include data encryptions, authentications, and key distributions and management. Select as many as possible correct answers. Note: you will receive negative points for incorrect answers.

a$.$

Cryptographic algorithms may be placed at the physical layer, making communications completely secure$.$

b$.$

Cryptographic algorithms may be placed at the application layer for securing user$-$to$-$user communications. This eliminates the need to update the TCP$/$IP protocol suite.

c$.$

Cryptographic algorithms may be placed at the IP layer for securing IP packets. Doing so needs to update the IP protocol suite.

d$.$

Cryptographic algorithms may be placed at the TCP layer for securing TCP packets. Doing so needs to update the TCP protocol suite.

e$.$

Cryptographic algorithms may be placed at the data$-$link layer for securing data frames. Doing so needs to update the data$-$link protocol suite.