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- 2071 Shrawan · 4 marks
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Short note: WEP
Short answer
WEP is the original 802.11 security scheme using RC4 with a 40/104-bit key plus 24-bit IV and CRC-32 integrity. Weaknesses include IV reuse, FMS key recovery, linear CRC, and no replay protection. It is obsolete, replaced by WPA/WPA2/WPA3.
Write a short note on WEP.
WEP (Wired Equivalent Privacy) is the original security algorithm of the IEEE 802.11 Wi-Fi standard (1997). It was meant to give a wireless LAN the same level of confidentiality as a wired LAN.
Operation
- Uses the RC4 stream cipher with a shared secret key of 40 or 104 bits.
- A 24-bit initialisation vector (IV) is added to the key (total 64 or 128 bits) to form the RC4 seed, and the IV is sent in plain text in each frame.
- Integrity: a 32-bit CRC-32 (Integrity Check Value) is appended to the data before encryption.
- Encryption: ciphertext = (data + ICV) XOR RC4 keystream.
- Authentication: open system or shared key (challenge-response).
IV + Key -> RC4 -> keystream
Data+CRC XOR keystream -> [IV | Ciphertext]
Weaknesses
- The IV is only 24 bits (2²⁴ = 16.7 million values), so it repeats quickly (after a few thousand packets by chance), and reused keystreams reveal the plaintext.
- FMS and other attacks recover the key from captured packets within minutes.
- CRC-32 is linear, so an attacker can modify messages without detection.
- No replay protection; no per-user keys; shared key authentication leaks keystream.
WEP is obsolete and was replaced by WPA (TKIP) and WPA2/WPA3 (AES-CCMP).
✓ Answer checked by Claude Opus 5.5 (high effort)