Briefly explain how WEP implementation violates the cardinal rule of cryptography: anything that creates a detectable pattern must be avoided.

Question

What will be an ideal response?

Answer 1

WEP implementation violates the cardinal rule of cryptography: anything that creates a detectable pattern must be avoided. This is because patterns provide an attacker with valuable information to break the encryption. The implementation of WEP creates a detectable pattern for attackers. IVs are 24-bit numbers, meaning there are 16,777,216 possible values. An AP transmitting at only 11 Mbps can send and receive 700 packets each second. If a different IV were used for each packet, then the IVs would start repeating in fewer than seven hours (a "busy" AP can produce duplicates in fewer than five hours). An attacker who captures packets for this length of time can see the duplication and use it to crack the code.

Yet it does not always require seven hours of capturing packets to see the IV repeat. Some wireless systems always start with the same IV after the system is restarted and then follow the same sequence of incrementing IVs.