Wi-Fi Protected Access
Wi-Fi Protected Access (WPA and WPA2) is a class of systems to secure wireless (Wi-Fi) computer networks. It was created in response to several serious weaknesses researchers had found in the previous system, Wired Equivalent Privacy (WEP). WPA implements the majority of the IEEE 802.11i standard, and was intended as an intermediate measure to take the place of WEP while 802.11i was prepared. WPA is designed to work with all wireless network interface cards, but not necessarily with first generation wireless access points. WPA2 implements the full standard, but will not work with some older network cards. Both provide good security, with two significant issues:
- either WPA or WPA2 must be enabled and chosen in preference to WEP. WEP is usually presented as the first security choice in most installation instructions.
- in the "Personal" mode, the most likely choice for homes and small offices, a passphrase is required that, for full security, must be longer than the typical 6 to 8 character passwords users are taught to employ.
History
WPA was created by The Wi-Fi Alliance, an industry trade group, which owns the trademark to the Wi-Fi name and certifies devices that carry that name.
WPA is designed for use with an IEEE 802.1X authentication server, which distributes different keys to each user; however, it can also be used in a less secure "pre-shared key" (PSK) mode, where every user is given the same passphrase.
Data is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV). One major improvement in WPA over WEP is the Temporal Key Integrity Protocol (TKIP), which dynamically changes keys as the system is used. When combined with the much larger IV, this defeats the well-known key recovery attacks on WEP.
In addition to authentication and encryption, WPA also provides vastly improved payload integrity. The cyclic redundancy check (CRC) used in WEP is inherently insecure; it is possible to alter the payload and update the message CRC without knowing the WEP key. A more secure message authentication code (usually known as a MAC, but here termed a MIC for "Message Integrity Code") is used in WPA, an algorithm named "Michael". The MIC used in WPA includes a frame counter, which prevents replay attacks being executed;
By increasing the size of the keys and IVs, reducing the number of packets sent with related keys, and adding a secure message verification system, WPA makes breaking into a Wireless LAN far more difficult. The Michael algorithm was the strongest that WPA designers could come up with that would still work with most older network cards; .
WPA2
WPA2 implements the mandatory elements of 802.11i. In particular, the Michael algorithm is replaced by a message authentication code, CCMP, that is considered fully secure and RC4 is replaced by AES. Official support for WPA2 in Microsoft Windows XP was rolled out on 1 May 2005. Driver upgrades for network cards may be required. Firmware upgrades needed are included in AirPort 4.2, released July 14, 2005. Note that from March 13, 2006, WPA2 certification is mandatory for all new devices wishing to be Wi-Fi certified.
Security in pre-shared key mode
Pre-shared key mode (PSK, also known as personal mode) is designed for home and small office networks that cannot afford the cost and complexity of an 802.1X authentication server. Each user must enter a passphrase to access the network. The passphrase may be from eight to 63 ASCII characters or 64 hexadecimal digits (256 bits). If you choose to use the ASCII characters, a hash function reduces it from 504 bits (63 characters * 8 bits/character) to 256 bits (using also the SSID). The passphrase may be stored on the user's computer at their discretion under most operating systems to avoid re-entry. The passphrase must remain stored in the Wi-Fi access point.
Security is strengthened by employing a PBKDF2 key derivation function. However, the weak passphrases users typically employ are vulnerable to password cracking attack. Password cracking can be defeated by using a passphrase of at least 5 Diceware words or 14 completely random letters with WPA and WPA2. For maximum strength, 8 Diceware words or 22 random characters should be employed. Passphrases should be changed at regular intervals, or whenever an individual with access is no longer authorized to use the network or when a device configured to use the network is lost or compromised.
Some consumer chip manufacturers have attempted to bypass weak passphrase choice by adding a method of automatically generating and distributing strong keys through a software or hardware interface that uses an external method of adding a new Wi-Fi adapter or appliance to a network. These methods include pushing a button (Broadcom SecureEasySetup and Buffalo AirStation One-Touch Secure System) and entering a short challenge phrase through software (Atheros JumpStart)
EAP types under WPA- and WPA2- Enterprise
The Wi-Fi alliance has announced the inclusion of additional EAP (Extensible Authentication Protocol) types to its certification programs for WPA- and WPA2- Enterprise. This was to ensure that WPA-Enterprise certified products can interoperate with one another. Previously, only EAP-TLS (Transport Layer Security) was certified by the Wi-Fi alliance.
The EAP types now included in the certification program are:
- EAP-TLS (previously tested)
- EAP-TTLS/MSCHAPv2
- PEAPv0/EAP-MSCHAPv2
- PEAPv1/EAP-GTC
- EAP-SIM
Other EAP types may be supported by 802.1X clients and servers developed by specific firms. This certification is an attempt for popular EAP types to interoperate; their failure to do so is currently one of the major issues preventing rollout of 802.1X on heterogeneous networks.
| Passphrase | |||
| A passphrase is a sequence of words or other text used to control access to a computer system, program or data... | |||
| PBKDF2 | |||
| PBKDF2 (Password-Based Key Derivation Function) is a key derivation function that is part of RSA Laboratories' Public-Key Cryptography Standards (PKCS) series... | |||
| WAPI | |||
| WAPI (WLAN Authentication and Privacy Infrastructure) is a Chinese National Standard for Wireless LAN (GB 15629.11-2003)... | |||
| Wired Equivalent Privacy | |||
| Wired Equivalent Privacy (WEP) is a scheme that is part of the IEEE 802.11 wireless networking standard to secure IEEE 802.11 wireless networks (also known as Wi-Fi networks)... | |||
| Wireless Access Point | |||
| In Computer Networking, a wireless access point (WAP or AP) is a device that connects wireless communication devices together to form a wireless network... | |||
| Wireless LAN | |||
| A wireless LAN or WLAN is a wireless local area network, which is the linking of two or more computers without using wires... | |||
