User's Manual Part 1

GN-A15AG Wireless Access Point User Guide

AES (Advanced Encryption Standard), A standard, sponsored by the

National Institute of Standards and Technology, for protecting data

through encryption. AES supports key sizes of 128 bits, 192 bits and

256 bits and will serve as a replacement for the Data Encryption

Standard (DES), which has a key size of 56 bits. In addition to the

increased security that comes with larger key sizes, AES can

encrypt data much faster than Triple-DES, a DES enhancement that

which essentially encrypts a message or document three times.

One of the biggest drawbacks to traditional WEP security is that

changing the encryption key is optional. Even if you do switch

encryption keys from time to time, there is no option for globally

rekeying all access points and all wireless NICs.

Instead, rekeying is a tedious manual process and is completely

impractical for large organizations. After all, the instant you rekey an

access point, none of the clients will be able to access it until they

are also rekeyed.

But with WPA, the rekeying of global encryption keys is required. In

the case of unicast traffic, the encryption key is changed after every

frame using Temporary Key Integrity Protocol (TKIP). This protocol

allows key changes to occur on a frame by frame basis and to be

automatically synchronized between the access point and the

wireless client. Global rekeying works by advertising the new keys to

wireless clients.

The TKIP is really the heart and soul of WPA security. TKIP replaces

WEP encryption. And although WEP is optional in standard Wi-Fi,

TKIP is required in WPA. The TKIP encryption algorithm is stronger

than the one used by WEP but works by using the same hardware-

based calculation mechanisms WEP uses.

The TKIP protocol actually has several functions. First, it determines

which encryption keys will be used and then verifies the client’s

security configuration. Second, it is responsible for changing the

unicast encryption key for each frame. Finally, TKIP sets a unique

starting key for each authenticated client that is using a preshared

key.

WPA PSK WPA use of a preshared key.