An integrity check value (ICV) lets a wireless receiver detect altered data. WEP appends a 32-bit checksum to each plaintext message before encrypting it, then verifies the value after decryption. section 20.1.2
Key implementation facts:
- WEP uses the ICV alongside RC4 encryption; integrity checking does not make WEP secure against its broader vulnerabilities. section 20.1.2
- TKIP replaces WEP’s weaker ICV with a stronger message integrity check (MIC) and adds sequence numbers to mitigate replay attacks. section 20.3.1
WEP message processing
For a transmitted plaintext message, WEP calculates a 32-bit ICV, appends it, and encrypts the combined data. The receiver decrypts the message and checks the ICV for evidence of tampering. section 20.1.2
