WEP: Wired Equivalent Privacy
It is the simple encryption technique which used the 40-bit key with the 24-bit initialisation vector and utilized the RC4 algorithm for encryption. It also used CRC-32 for integrity check mechanism; because the initialisation vector was very small, there was a possibility that the IV’s getting reused. This weakness caused the algorithm to be broken easily.
WPA: Wi-Fi Protected Access
This algorithm uses 48 bit IV and is based on the 802.11i standard. The RC4 algorithm used temporal keys of 128-bit size and 64 bit MIC check which made the encryption stronger than WEP. Here 128-bit temporal keys, mixed with 48 bit IV and MAC address of the sender create the key stream to encrypt the data using RC4. Temporal keys are changed every 10,000 packets.
WPA2: Wi-fi Protected Access with EAP
This is for enterprise use with strong data protection and network access control. Here, instead of RC4, AES (Advanced encryption standard) is used for encryption with temporal keys. The key size is 128-bit keys. It makes use of centralised RADIUS server for authentication.