CompTIA Security+ Question A-90

Which of the following protocols is vulnerable to man-in-the-middle attacks by NOT using end to end TLS encryption?

D. WPA 2

Answer: B

WEP offers no end-to-end TLS encryption.

The WEP process consists of a series of steps as follows: The wireless client sends an authentication request. The Access Point (AP) sends an authentication response containing clear-text (uh-oh!) challenge text. The client takes the challenge text received and encrypts it using a static WEP key. The client sends the encrypted authentication packet to the AP. The AP encrypts the challenge text using its own static WEP key and compares the result to the authentication packet sent by the client. If the results match, the AP begins the association process for the wireless client.

The big issue with WEP is the fact that it is very susceptible to a Man in the Middle attack. The attacker captures the clear-text challenge and then the authentication packet reply. The attacker then reverses the RC4 encryption in order to derive the static WEP key. Yikes! As you might guess, the designers attempted to strengthen WEP using the approach of key lengths. The native Windows client supported a 104-bit key as opposed to the initial 40-bit key. The fundamental weaknesses in the WEP process still remained however.