How WEP works - Part One

As you probably already know Wired Equivalent Privacy (WEP) is used by companies to secure their wireless connections from sniffing attacks. You’ve probably also heard that it’s not very secure. In the first part of this 2 part series I’ll explain the inner workings of WEP and follow it up next month with why it’s insecure.

WEP uses the RC4 algorithm to encrypt the packets of information as they are sent out from the access point or wireless network card. As soon as the access point receives the packets sent by the user’s network card it decrypts them. Each byte of data will be encrypted using a different packet key. This ensures that if a hacker does manage to crack this packet key the only information that is leaked is that which is contained in that packet.

The actual encryption logic in RC4 is very simple. The plain text is XOR-ed with an infinitely long keystream. The security of RC4 comes from the secrecy of the packet key that’s derived from the keystream.