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Aircrack-ng is a network software suite consisting of a detector, packet sniffer, WEP and WPA/WPA2-PSK cracker and analysis tool for 802.11 wireless LANs.It works with any wireless network interface controller whose driver supports raw monitoring mode and can sniff 802.11a, 802.11b and 802.11g traffic.
A 128-bit WEP key is usually entered as a string of 26 hexadecimal characters. 26 digits of 4 bits each gives 104 bits; adding the 24-bit IV produces the complete 128-bit WEP key (4 bits × 26 + 24-bit IV = 128-bit WEP key). Most devices also allow the user to enter it as 13 ASCII characters (8 bits × 13 + 24-bit IV = 128-bit WEP key). 152-bit ...
After enough packets have been collected, the program can then compute the key for the wireless network. As the software makes use of brute-force attack however, cracking the encryption can take between a few hours to several days, based on the activity on the network. [3]
The four-way handshake [8] is designed so that the access point (or authenticator) and wireless client (or supplicant) can independently prove to each other that they know the PSK/PMK, without ever disclosing the key. Instead of disclosing the key, the access point (AP) and client encrypt messages to each other—that can only be decrypted by ...
WEP was superseded in 2003 by WPA, a quick alternative at the time to improve security over WEP. The current standard is WPA2; [3] some hardware cannot support WPA2 without firmware upgrade or replacement. WPA2 uses an encryption device that encrypts the network with a 256-bit key; the longer key length improves security over WEP.
WEP used a 64-bit or 128-bit encryption key that must be manually entered on wireless access points and devices and does not change. TKIP employs a per-packet key, meaning that it dynamically generates a new 128-bit key for each packet and thus prevents the types of attacks that compromised WEP. [4]
In order to mount a brute-force or dictionary based WPA password cracking attack on a Wi‑Fi user with WPA or WPA2 enabled, a hacker must first sniff the WPA 4-way handshake.
To prevent this from happening, WEP includes a 24-bit initialization vector (IV) in each message packet. The RC4 key for that packet is the IV concatenated with the WEP key. WEP keys have to be changed manually and this typically happens infrequently. An attacker therefore can assume that all the keys used to encrypt packets share a single WEP key.