Complex sentence: First, there is the wireless connection between the client and the access point, which needs to be encrypted, so that the connection cannot be eavesdropped or attacked by a man-in-the-middle-attack.
Split into simpler sentences: First, there is the wireless connection between the client and the access point. This needs to be encrypted, so that the connection cannot be eavesdropped or attacked by a man-in-the-middle-attack.