I use this as a reminder.

Wireless: Open and Shared-Key Authentication

Both authentication methods were developed for the old WEP security standard. Only Open can be used with the newer and more secure WPA2 standard.

Shared-Key leverages a challenge packet sent from the AP to the client. The client must supply a correct WEP key, encrypt it and send it back. That packet can easily be captured and deciphered by a sniffer.

Bottom line is that Shared-Key is no longer used. Use the Open authentication method paired with a strong authentication backend such as RADIUS or WPA2 with AES encryption.