Aircrack-ng Git

[Michael]

Thistutorial walks you through cracking WPA/WPA2 networks which use pre-shared keys. I recommend you do some background reading to better understand what WPA/WPA2 is. The Wiki links page has a WPA/WPA2 section. The best document describing WPA is Wi-Fi Security - WEP, WPA and WPA2. This is the link to download the PDF directly. The WPA Packet Capture Explained tutorial is a companion to this tutorial.

WPA/WPA2 supports many types of authentication beyond pre-shared keys. aircrack-ng can ONLY crack pre-shared keys. So make sure airodump-ng shows the network as having the authentication type of PSK, otherwise, don't bother trying to crack it.

There is another important difference between cracking WPA/WPA2 and WEP. This is the approach used to crack the WPA/WPA2 pre-shared key. Unlike WEP, where statistical methods can be used to speed up the cracking process, only plain brute force techniques can be used against WPA/WPA2. That is, because the key is not static, so collecting IVs like when cracking WEP encryption, does not speed up the attack. The only thing that does give the information to start an attack is the handshake between client and AP. Handshaking is done when the client connects to the network.Although not absolutely true, for the purposes of this tutorial, consider it true. Since the pre-shared key can be from 8 to 63 characters in length, it effectively becomes impossible to crack the pre-shared key.

The only time you can crack the pre-shared key is if it is a dictionary word or relatively short in length. Conversely, if you want to have an unbreakable wireless network at home, use WPA/WPA2 and a 63 character password composed of random characters including special symbols.

The impact of having to use a brute force approach is substantial. Because it is very compute intensive, a computer can only test 50 to 300 possible keys per second depending on the computer CPU. It can take hours, if not days, to crunch through a large dictionary. If you are thinking about generating your own password list to cover all the permutations and combinations of characters and special symbols, check out this brute force time calculator first. You will be very surprised at how much time is required.

IMPORTANT This means that the passphrase must be contained in the dictionary you are using to break WPA/WPA2. If it is not in the dictionary then aircrack-ng will be unable to determine the key.

It is recommended that you experiment with your home wireless access point to get familiar with these ideas and techniques. If you do not own a particular access point, please remember to get permission from the owner prior to playing with it.

In the response above, you can see that ath0 is in monitor mode, on the 2.452GHz frequency which is channel 9 and the Access Point shows the MAC address of your wireless card. Only the madwifi-ng drivers show the card MAC address in the AP field, other drivers do not. So everything is good. It is important to confirm all this information prior to proceeding, otherwise the following steps will not work properly.

Notice that airmon-ng enabled monitor-mode on mon0. So, the correct interface name to use in later parts of the tutorial is mon0. Wlan0 is still in regular (managed) mode, and can be used as usual, provided that the AP that wlan0 is connected to is on the same channel as the AP you are attacking, and you are not performing any channel-hopping.

Here, mon0 is seen as being in monitor mode, on channel 9 (2.452GHz). Unlike madwifi-ng, the monitor interface has no Access Point field at all. Also notice that wlan0 is still present, and in managed mode - this is normal. Because both interfaces share a common radio, they must always be tuned to the same channel - changing the channel on one interface also changes channel on the other one.

This step is optional. If you are patient, you can wait until airodump-ng captures a handshake when one or more clients connect to the AP. You only perform this step if you opted to actively speed up the process. The other constraint is that there must be a wireless client currently associated with the AP. If there is no wireless client currently associated with the AP, then you have to be patient and wait for one to connect to the AP so that a handshake can be captured. Needless to say, if a wireless client shows up later and airodump-ng did not capture the handshake, you can backtrack and perform this step.

This step sends a message to the wireless client saying that that it is no longer associated with the AP. The wireless client will then hopefully reauthenticate with the AP. The reauthentication is what generates the 4-way authentication handshake we are interested in collecting. This is what we use to break the WPA/WPA2 pre-shared key.

The purpose of this step is to actually crack the WPA/WPA2 pre-shared key. To do this, you need a dictionary of words as input. Basically, aircrack-ng takes each word and tests to see if this is in fact the pre-shared key.

When this happens you either have to redo step 3 (deauthenticating the wireless client) or wait longer if you are using the passive approach. When using the passive approach, you have to wait until a wireless client authenticates to the AP.

Unfortunately, sometimes you need to experiment a bit to get your card to properly capture the four-way handshake. The point is, if you don't get it the first time, have patience and experiment a bit. It can be done!

In an ideal world, you should use a wireless device dedicated to capturing the packets. This is because some drivers such as the RTL8187L driver do not capture packets the card itself sends. Also, always use the driver versions specified on the wiki. This is because some older versions of the drivers such as the RT73 driver did not capture client packets.

To dig deep into the packet analysis, you must start airodump-ng without a BSSID filter and specify the capture of the full packet, not just IVs. Needless to say, it must be locked to the AP channel. The reason for eliminating the BSSID filter is to ensure all packets including acknowledgments are captured. With a BSSID filter, certain packets are dropped from the capture.

When it comes to analyzing packet captures, it is impossible to provide detailed instructions. I have touched on some techniques and areas to look at. This is an area which requires effort to build your skills on both WPA/WPA2 plus how to use Wireshark.

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. Packages are released for Linux and Windows.[2]

Aircrack-ng is a fork of the original Aircrack project. It can be found as a preinstalled tool in many security-focused Linux distributions such as Kali Linux or Parrot Security OS,[3] which share common attributes as they are developed under the same project (Debian).[4]

Aircrack was originally developed by French security researcher Christophe Devine,[5] its main goal was to recover 802.11 wireless networks WEP keys using an implementation of the Fluhrer, Mantin and Shamir (FMS) attack alongside the ones shared by a hacker named KoreK.[6][7][8]

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.[10] 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.[11]

Due to U.S. restrictions on the export of cryptographic algorithms, WEP was effectively limited to 64-bit encryption.[12] 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.[13][14]

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.[15]

The IV is constrained to 24 bits, which means that its maximum values are 16,777,216 (224), regardless of the key size.[16] Since the IV values will eventually be reused and collide (given enough packets and time), WEP is vulnerable to statistical attacks.[17] William Arbaugh notes that a 50% chance of a collision exists after 4823 packets.[18]

In 2003, the Wi-Fi Alliance announced that WEP had been superseded by Wi-Fi Protected Access (WPA). In 2004, with the ratification of the full 802.11i standard (i.e. WPA2), the IEEE declared that both WEP and WEP2 have been deprecated.[19]

Wi-Fi Protected Access (WPA) was designed to be implemented through firmware updates rather than requiring dedicated hardware.[20] 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:

In WPA-PSK, each packet was individually encrypted using the IV information, the MAC address, and the pre-shared key as inputs. The RC4 cipher was used to encrypt the packet content with the derived encryption key.[22]

Additionally, WPA introduced WPA Enterprise, which provided enhanced security for enterprise-level networks. WPA Enterprise employed a more robust authentication mechanism known as Extensible Authentication Protocol (EAP). This mode required the use of an Authentication Server (AS) such as RADIUS (Remote Authentication Dial-In User Service) to validate user credentials and grant access to the network.

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