End-to-end encryption is used by users, and link encryption is used by service providers. Which of the following correctly describes these technologies?

A.
Link encryption does not encrypt headers and trailers.

B.
Link encryption encrypts everything but data link messaging.

C.
End-to-end encryption requires headers to be decrypted at each hop.

D.
End-to-end encryption encrypts all headers and trailers.

Explanation:
B: Encryption can be performed at different communication levels, each with different types of protection and implications. Two general modes of encryption implementation are link
encryption and end-to-end encryption. Link encryption encrypts all the data along a specific communication path, as in a satellite link, T3 line, or telephone circuit. Not only is the user
information encrypted, but the header, trailers, addresses, and routing data that are part of the packets are also encrypted. The only traffic not encrypted in this technology is the data
link control messaging information, which includes instructions and parameters that the different link devices use to synchronize communication methods. Link encryption provides
protection against packet sniffers and eavesdroppers. In end-to-end encryption, the headers, addresses, routing, and trailer information are not encrypted, enabling attackers to learn
more about a captured packet and where it is headed. With end-to-end encryption only the data payload is encrypted.
A is incorrect because link encryption does encrypt the headers and trailers. This is a major advantage to using link encryption: the headers, trailers, and data payload are encrypted
except for the data link messaging. It also works seamlessly at a lower layer in the OSI model, so users do not need to do anything to initiate it.
C is incorrect because the headers are not encrypted with end-to-end encryption, so there is no need to decrypt them at each hop. This is an advantage of using end-to-end
encryption. Other advantages include additional flexibility for the user in choosing what gets encrypted and how, and a higher granularity of functionality because each application or
user can choose specific configurations.
D is incorrect because end-to-end encryption does not encrypt any headers or trailers. As a result, they are not protected. This is the primary disadvantage to using end-to-end
encryption. If the headers and trailers need to be protected, then link encryption should be used.