5. Gaining Access - WEP Cracking

Basics

• WEP means: Wired Equvalent Privacy
• It's an old encryption
• Uses an algorythm called RC4
• Still used in some networks
• Can be cracked easily

How Encryption works

• Each Package is encrypted via a unique Keystream
• Random Initialization Vector (IV) is used to generate the Keystreams
• The IV is only 24 bits
• IV + (password) Key = keystream

WEP Cracking

• IV is too small (24bits)
• IV is sent in plain text

Weakness

• IV's will repeat on busy networks
• This will make WEP vulnerable to statistical attacks
• Repeated IV's can be used to determine the Keystream
• And break the encryption

Because the router already knows the (password) Key WLAN devices just need to send the IV