Wireless Security Protocols

Wireless security protocols are sets of cryptographic rules that protect data transmitted over Wi-Fi networks. Unlike wired networks, where physical access to the cable provides some security, wireless signals propagate through the air and can be intercepted by anyone within range. Without encryption and authentication, an attacker could eavesdrop on all traffic, inject malicious frames, or impersonate legitimate users. The protocols define how devices (stations) and access points (APs) authenticate each other and encrypt data frames.

WEP (Wired Equivalent Privacy) – Introduced in 1997 as part of the original 802.11 standard. It uses the RC4 stream cipher with either 40-bit or 104-bit keys (combined with a 24-bit initialization vector, IV, for a total of 64 or 128 bits). The IV is sent in plaintext, and because RC4 is a stream cipher, keystream reuse is catastrophic. WEP has no key management; the same static key is used by all clients. An attacker can capture packets and use tools like aircrack-ng to recover the key after collecting enough IVs (typically 20,000–40,000). WEP is considered broken and should never be used.

WPA (Wi-Fi Protected Access) – Released in 2003 as a stopgap after WEP's weaknesses became widely known. It uses TKIP (Temporal Key Integrity Protocol) which still uses RC4 but adds per-packet key mixing, a message integrity check (MIC, called Michael), and a rekeying mechanism. TKIP changes the encryption key for every packet, preventing the IV collision attacks that broke WEP. However, TKIP has its own vulnerabilities, such as the Beck-Tews attack (2008) which can decrypt small packets, and the more serious Hole196 vulnerability. WPA also introduced 802.1X authentication for enterprise networks, using EAP (Extensible Authentication Protocol) and a RADIUS server.

WPA2 (Wi-Fi Protected Access 2) – Ratified in 2004 with 802.11i. It replaces TKIP with CCMP (Counter Mode CBC-MAC Protocol) based on AES (Advanced Encryption Standard) with a 128-bit key. AES-CCMP provides strong encryption and integrity. The 4-way handshake is used to derive pairwise transient keys (PTK) from a pairwise master key (PMK). WPA2 can operate in two modes: - Personal (PSK): Uses a pre-shared key (passphrase) that is hashed to produce the PMK. Any client knowing the passphrase can connect. - Enterprise (802.1X): Uses a RADIUS server for authentication, with the PMK derived from EAP authentication. This provides per-user keys and centralized control.

WPA2 is still widely used but is vulnerable to KRACK (Key Reinstallation Attack, 2017) which exploits the 4-way handshake to force nonce reuse, allowing decryption of some packets. Also, dictionary attacks against the PSK are possible if the attacker captures the 4-way handshake.

WPA3 (Wi-Fi Protected Access 3) – Announced in 2018 and mandatory for new devices since 2020. WPA3 introduces: - SAE (Simultaneous Authentication of Equals): Replaces the PSK-based 4-way handshake. SAE uses a Dragonfly handshake based on the Diffie-Hellman key exchange, which provides forward secrecy and is resistant to offline dictionary attacks. An attacker cannot brute-force the passphrase after capturing the handshake. - 192-bit security suite: For enterprise networks, WPA3-Enterprise uses 192-bit AES-GCMP (Galois/Counter Mode Protocol) and mandates EAP-TLS with a secure key derivation. - OWE (Opportunistic Wireless Encryption): For open networks, OWE provides encryption without authentication (like a captive portal scenario). It uses Diffie-Hellman to derive a session key, preventing passive eavesdropping.

The 4-way handshake is the core mechanism that establishes encryption keys between a client and AP. It assumes both parties already have the PMK (from PSK or 802.1X).

In WPA3, the handshake is replaced by SAE, which uses a commit-and-confirm exchange to establish a shared secret without exposing the password to offline attack.

- WEP: RC4 - WPA: TKIP (RC4) - WPA2: CCMP (AES) - WPA3: GCMP-256 (AES) for enterprise; CCMP-128 for personal - Key lengths:

- WEP: 64 or 128 bits (including IV) - WPA: 128-bit temporal key - WPA2: 128-bit AES key - WPA3: 128-bit (personal) or 192-bit (enterprise) - Authentication:

- Open: no authentication - Shared Key (WEP): uses challenge-response with RC4 (broken) - PSK: passphrase (8–63 ASCII characters) hashed to PMK - 802.1X: RADIUS server with EAP methods (EAP-TLS, PEAP, EAP-FAST) - Group key rotation: Default every 86400 seconds (24 hours) for WPA2; configurable. - PMK lifetime: For 802.1X, determined by RADIUS session timeout (default 3600 seconds).

On a Cisco wireless LAN controller (WLC), configure a WPA2-PSK SSID:

config wlan security wpa enable 1
config wlan security wpa wpa2 ciphers aes enable 1
config wlan security wpa akm psk set-key ascii MySecurePassphrase 1
config wlan security wpa akm psk enable 1

On a Linux host using wpa_supplicant, the configuration file (/etc/wpa_supplicant/wpa_supplicant.conf) looks like:

network={
    ssid="MySSID"
    psk="MyPassphrase"
    proto=RSN
    pairwise=CCMP
    group=CCMP
}

To verify the security protocol in use on a client:

Wireless security protocols interact with: - RADIUS: In WPA2/3-Enterprise, the AP acts as a RADIUS client, forwarding authentication requests to the server. - EAP: Various EAP methods (EAP-TLS, PEAP, EAP-FAST) transport authentication data over 802.1X. - 802.1X: Provides port-based access control; the AP blocks all traffic until authentication succeeds. - Captive portals: Often used with open networks; OWE in WPA3 adds encryption before the portal. - Fast roaming: Protocols like 802.11r (Fast BSS Transition) reduce re-authentication delay by caching keys.

N10-009 tests:

Common wrong answers: confusing TKIP with AES, thinking WPA2 uses TKIP by default, or believing WPA3 uses the same 4-way handshake as WPA2.

A large corporation with 5000 employees deploys WPA2-Enterprise using a Cisco WLC and a RADIUS server (e.g., Cisco ISE). Each employee has a unique username/password or certificate. The SSID is configured with AES only (TKIP disabled) to avoid mixed-mode vulnerabilities. The RADIUS server enforces 802.1X with PEAP-MSCHAPv2. When an employee connects, their device performs the 4-way handshake with the AP, but the PMK comes from the RADIUS server after successful EAP authentication. This provides per-user keys: even if one employee's credentials are compromised, other users are not affected. The network team sets a RADIUS session timeout of 8 hours, forcing re-authentication after that period. They also enable 802.11r for fast roaming, reducing handoff latency to under 20 ms. A common issue is certificate validation errors: if the RADIUS server's certificate is not trusted by the client, authentication fails. The team must ensure the CA certificate is deployed to all devices via MDM or GPO.

A small business with 20 employees uses WPA2-PSK with a strong passphrase (20+ random characters). The AP is a consumer-grade device. The main risk is that the passphrase is shared among all employees; if an employee leaves, the passphrase must be changed on all devices. Also, the PSK is vulnerable to offline dictionary attacks if the 4-way handshake is captured. To mitigate, the business should enable PMF (Protected Management Frames) if supported, and disable WPS (Wi-Fi Protected Setup) which can be brute-forced in hours. A common mistake is using a weak passphrase like the company name, which can be cracked quickly.

A coffee shop wants to provide free Wi-Fi without a password but still protect customers from eavesdropping. They deploy WPA3-OWE (Opportunistic Wireless Encryption). When a customer connects, their device performs an unauthenticated Diffie-Hellman exchange with the AP, establishing a unique session key. All traffic is encrypted, preventing passive sniffing. However, there is no authentication, so the AP cannot prevent unauthorized use. The coffee shop uses a captive portal for terms of service acceptance. A common misconfiguration is that older devices without WPA3 support will see the network as 'open' but cannot connect via OWE; the AP must be configured to allow fallback to open for legacy devices, which negates encryption. The solution is to have two SSIDs: one for WPA3-OWE and one for legacy open (with a warning).