Use of Integrity protection in LTE?

Question

For confirmation purpose only, I want to know the use of integrity protection. As per my understanding integrity protection is only needed to verify Security-Mode-Command/Security-Mode-Complete messages? Because all subsequent messages are encrypted and any "man in the middle attack" will result in decryption failure at the other end.

Is my understanding correct?

Answer 1

Yes, your understanding is correct. I just want to add some more information. The purpose of integrity is to make sure that data is not damaged by mistake like due to additional signal etc. Between a sender and receiver anyone can read data like wireshark captures the logs whereas encryption changes the actual data i.e. known as encrypted data and receiver decrypt the data. Even if someone is in between sender and receiver that person or thing can't read the data.

Security mode command message is an integrity protected message whereas security mode complete message is integrity protected as well as ciphered. Both are necessary to transfer the information successfully between the sender and receiver.