Wireless Security

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Quick Summary

The standards are pretty confusing. Here ia a map showing the various relationships.

<u>Encryption Choices:</u>

<ul> <li>None - Obvously, NONE isn't really a valid choice.</li>

<li>WEP - Wired Equivalent Privacy can be easily cracked and provides very limited protection.</li>

<li>TKIP - Temporal Key Integrity Protocol replaced WEP and uses the RC4 cipher on each packet instead of the whole session. (... which was WEP's weakness, given enough packets, the key WEP can be discovered.)</li>

<li>CCMP - AES in Counter mode with Chain Block Cipher and Media Access Control replaces TKIP. FIPS-140-2 requires AES for the federal government. So there really isn't a choice for an encryption scheme - it's AES (CCMP).</li> </ul>

<u>Authentication Choices:</u>

<ul> <li>None probably isn't a choice.</li> <li>WPA-PSK (Wifi Protected Access with Pre Shared Key) authenticates the network session using a key, which is known to both sides. The key must be 8-63 ascii characters in length. WPA-PSK can be cracked through a brute force dictionary attack. Thus, it's only as strong as the password. Most people recommend >20 characters and a complex passphrase.</li> <li>802.1x EAP (extended authentication protocol) authenticates the user and requires a PKI certificate.</li> </ul>

What is Acceptable?

So we have two acceptable modes of security. Both modes are supported by XP.

WPA-PSK with AES - This is acceptable, but the pre shared key must be strong to resist dictionary attacks. Most wireless nodes will provide this security mode.

WPA2 with AES and 802.1x EAP - This is the best, but is significantly more complicated because it requires a way to manage user accounts and PKI certificates. User accounts are usually handled through a RADIUS server, which can be internal to the wireless node or externally hosted on another server. The PKI certificates can be self-signed, which requires a way to generate the x.509 certs. They can also be provided by an external vendor, such as Verisign.

Federal Government

For the Federal Government, FIPS-140-2 is mandatory. At one point, this seemed to mean AES was sufficient, however, there is a list at http://csrc.nist.gov/cryptval/140-1/140val-all.htm, which shows the vendors/products with approved cryptographic modules. There really aren't a lot of vendors and the inexpensive routers, linksys, buffalo, etc. aren't part of the list.

  • Fortress Technologies, Air Fortress
  • 3e Technologies, 3e-523-F2
  • Cisco, Aironet
  • Aruba Wireless Networks
  • Symbol, WTLS Cryptographic Module in the AirBEAM® Safe product

For DoD, there really isn't a choice, wireless deployments are covered by a Security Technical Implementation Guideline STIG, corresponding policy 8100.2 and supplemental policy. The STIG is available here: http://iase.disa.mil/stigs/stig/wireless-stig-v5r1-final20feb07.pdf. High level requirements are as follows:

  • WiFi certified
  • NIAP Common Criteria Certification
  • Aproved by the DAA
  • Interoperability as determined by the JTIC
  • 802.11 compliant using WPA2 and 802.1x with EAP-TLS
  • AES Counter with Cipher Block Chaining - Message Authentication Protocol (AES-CCMP)
  • Two factor authentication
  • Mandatory rogue access point detection
  • Wireless IDS
  • FIPS 140-2 Cryptographic Module Validation Program (level 2 if keys are stored in publicly accessible areas)
  • Personal firewalls in place for clients
  • Anti-Virus on clients
  • Wireless Intrusion Detection Systems with continuous scans and location sensing for rouge devices

Security Levels

Use the right level of security. The bottom line is - use either WPA-PSK or WPA2 (802.11i.) WPA-PSK is fine for most deployments, but WPA2 can be used for higher security.

Level 1: Field Stations or Field Deployment

Use WPA (WiFi protected Access) with AES - for encryption. WPA PSK (pre-shared key) is OK for home offices. WPA PSK can be cracked, but using a strong password helps a lot. Use >20 characters you wouldn't find in a dictionary. No specific user authentication required.

Level 2: Major Office

WPA with AES plus user authentication via 802.1x and PEAP (Protected Extensible Authentication Protocol) or TTLS (Tunneled Transport Layer Securit.) 802.1x = EAP. Do not use Cisco's LEAP. Needs a radius server, with a server side certificate. Windows does not have a client for TTLS, so looks like the best bet is PEAP-EAP-MSCHAPv2. (i.e. 802.1x with protected EAP and CHAP)

Level 3: Large WiFi Deployments

WPA with AES plus authentication using 802.1x and PEAP over TLS. Autentication requires valid server side Certs (i.e. not self signed) EAP-TLS or PEAP-EAP-TLS with client side certs. (Soft certs OK). Use PKI best practices. Will require additional XP WPA suplicant.

Level 4: Military Grade

WPA with AES plus user authentication (802.1x-PEAP-TLS) using hardware tokens.