WEP Wired Equivalent Privacy was the first security
algorithm to be released, with the intention of providing data confidentiality comparable to that of a traditional wired
network. It was introduced in 1997 as part of the IEEE 802.11 technical standard and based on the
RC4 cipher and the
CRC-32 checksum algorithm for
integrity. Due to U.S. restrictions on the
export of cryptographic algorithms, WEP was effectively limited to 64-
bit encryption. Of this, 40 bits were allocated to the key and 24 bits to the
initialization vector (IV), to form the RC4 key. After the restrictions were lifted, versions of WEP with a stronger encryption were released with 128 bits: 104 bits for the
key size and 24 bits for the initialization vector, known as WEP2. The initialization vector works as a
seed, which is prepended to the key. Via the
key-scheduling algorithm (KSA), the seed is used to initialize the RC4 cipher's state. The output of RC4's
pseudo random generation algorithm (PRGA) follows a
XOR operation in combination with the
plaintext, and produces the
ciphertext. The IV is constrained to 24 bits, which means that its maximum values are 16,777,216 (224), regardless of the key size. Since the IV values will eventually be reused and
collide (given enough packets and time), WEP is vulnerable to statistical attacks. William Arbaugh notes that a 50% chance of a collision exists after 4823 packets.
WPA Wi-Fi Protected Access (WPA) was designed to be implemented through
firmware updates rather than requiring dedicated hardware. While still using RC4 at its core, it introduced significant improvements over its predecessor. WPA included two modes: WPA-PSK (WPA Personal) and WPA Enterprise. WPA-PSK (Wi-Fi Protected Access Pre-Shared Key), also known as WPA Personal, used a variant of the
Temporal Key Integrity Protocol (TKIP) encryption protocol. It improved security by implementing the following features: • A 56-bit cryptographic
message integrity code (MIC) called
Michael, compared to the 32-bit CRC-32 used in WEP. • An
initialization vector (
IV) sequencing discipline designed to prevent
replay attacks. • A
rekeying method to prevent key reuse. TKIP allocated 48 bits to the IV compared to the 24 bits of WEP, so the maximum number is 281,474,976,710,656 (248).
WPA2 WPA2 (Wi-Fi Protected Access 2) was developed as an upgrade to the original WPA standard and ratified in 2004, and became mandatory for Wi-Fi certified products in 2006. Like WPA, WPA2 provides two modes: WPA2-PSK (WPA2 Personal) and WPA2 Enterprise. Unlike WPA, WPA2-PSK uses the more secure
Advanced Encryption Standard (AES) in
CCM mode (Counter-Mode-CBC-MAC Protocol), instead of
TKIP. A backward compatible version, called WPA/WPA2 (Personal) still made use of TKIP. WPA2-PSK replaces the message integrity code
Michael with
CCMP. In July 2001, Borisov et al. published a comprehensive paper on the status of WEP and its various vulnerabilities. However, other researchers implemented the attack and were able to demonstrate the protocol's insecurity. The name of the attack derives from its inherent working: a packet is intercepted, "chops" off a part of it and sends a modified version to the Access Point, who will drop it if not valid. By repeatedly trying multiple values, the message can gradually be decrypted. The Chopchop attack was later improved by independent researchers. In 2005, security researcher Andrea Bittau presented the paper
The Fragmentation Attack in Practice. The homonymous attack exploits the fact that WEP splits the data into smaller fragments, which are reassembled by the receiver. Taking advantage of the fact that at least part of the plaintext of some packets
may be known, and that the fragments may have the same IV, data can be injected at will, flooding the network to statistically increase the chances of recovering the key.
WPA The first known attack on WPA was described by Martin Beck and Erik Tews in November 2008. They described an attack against TKIP in the paper
Practical Attacks Against WEP and WPA. The proof of concept resulted in the creation of
tkiptun-ng. In 2009, their attack was improved and demonstrated by a research group from Norway. == Features ==