Keep in mind, that as the fudge factor gets larger, the number of secret keys to try goes up tremendously and consequently the elapsed time also increases. Therefore with more available data, the need to brute force, which is very CPU and time intensive, can be minimized. For cracking WEP keys, a dictionary method is also included. For WEP, you may use either the statistical method described above or the dictionary method, not both at the same time.
With the dictionary method, you first create a file with either ascii or hexadecimal keys. A single file can only contain one type, not a mix of both. This is then used as input to aircrack-ng and the program tests each key to determine if it is correct. The only way to crack these pre-shared keys is via a dictionary attack.
This capability is also included in aircrack-ng. With pre-shared keys, the client and access point establish keying material to be used for their communication at the outset, when the client first associates with the access point.
There is a four-way handshake between the client and access point. Using input from a provided word list dictionary , aircrack-ng duplicates the four-way handshake to determine if a particular entry in the word list matches the results the four-way handshake.
If it does, then the pre-shared key has been successfully identified. It should be noted that this process is very computationally intensive and so in practice, very long or unusual pre-shared keys are unlikely to be determined. A good quality word list will give you the best results. Another approach is to use a tool like john the ripper to generate password guesses which are in turn fed into aircrack-ng.
The best explanation is an example. We will look at a specific byte. All bytes are processed in the same manner. You have the votes like in the screen shot above. For the first byte they look like: AE 50 11 20 71 20 10 12 84 The AE, 11, 71, 10 and 84 are the possible secret key for key byte 0. The numbers in parentheses are the votes each possible secret key has accumulated so far.
Now if you decide to use a fudge factor of 3. Aircrack-ng takes the vote from the most possible byte AE 50 :. Aircrack-ng will test brute force all possible keys with a vote greater than You can specify multiple input files either in. See Other Tips for examples. Also, you can run both airodump-ng and aircrack-ng at the same time: aircrack-ng will auto-update when new IVs are available.
The simplest case is to crack a WEP key. If you want to try this out yourself, here is a test file. The key to the test file matches the screen image above, it does not match the following example. If there were multiple networks contained in the file then you are given the option to select which one you want.
By default, aircrack-ng assumes bit encryption. Next, we look at cracking WEP with a dictionary. In order to do this, we need dictionary files with ascii or hexadecimal keys to try.
Remember, a single file can only have ascii or hexadecimal keys in it, not both. WEP keys can be entered in hexadecimal or ascii. The following table describes how many characters of each type is required in your files. Lets look at a PTW attack example. As well, it only works for 64 and bit WEP encryption.
Notice in this case that since there are multiple networks we need to select which one to attack. We select number 2. The program then responds:. Aircrack-ng is compiled with multiple optimizations based on CPU features we call crypto engines. A generic optimization is always available no matter what architecture it is compiled on or for. When running aircrack-ng, it will load the fastest optimization based on what your CPU supports.
For package maintainers, it is very useful as they don't have to target the one supporting all the CPU which would be the slowest.
Cracking can sometimes take a very long time and it is sometimes necessary to turn off the computer or put it to sleep for a while. In order to handle this kind of situation, a new set of option has been created. This needs updating for v1. Having said that, there are some techniques to improve your chances of finding the WEP key quickly. There is no single magic set of steps. The following describes some approaches which tend to yield the key faster. Unless you are comfortable with experimentation, leave well enough alone and stick to the simple approach.
NOTE: -z is the default attack mode in aircrack-ng v1. The overriding technique is capture as much data as possible. That is the single most important task. The number of initialization vectors IVs that you need to determine the WEP key varies dramatically by key length and access point. Typically you need , or more unique IVs for 64 bit keys and 1.
Clearly a lot more for longer key bit lengths. Then there is luck. There will be times that the WEP key can be determined with as few as 50, IVs although this is rare. If you start too early, aircrack tends to spend too much time brute forcing keys and not properly applying the statistical techniques. If they are using a 64 bit WEP, it can usually be cracked in less then 5 minutes generally less then 60 seconds with relatively few IVs.
It is surprising how many APs only use 64 bit keys. Once you hit , IVs, switch to testing bit keys. If it is as slow as SHA then it will take 20 days on AWS g2 x8 large for 8 characters made of alphanumeric or some 10 other symbols. Hacker News new past comments ask show jobs submit. Qub3d on July 24, parent next [—] Yeah, which is why it is sometimes weirdly safer to not change your SSID - a cracker can assume that someone who figured out how to change the broadcast name could've also changed the WiFi password So make sure airodump-ng shows the network as having the authentication type of PSK, otherwise, don't bother trying to crack it.
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.
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 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. If it is not in the dictionary then aircrack-ng will be unable to determine the key. The authentication methodology is basically the same between them. So the techniques you use are identical. 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.
Please send me any constructive feedback, positive or negative. Additional troubleshooting ideas and tips are especially welcome. Ensure all of the above assumptions are true, otherwise the advice that follows will not work. You should gather the equivalent information for the network you will be working on.
Then just change the values in the examples below to the specific network. This can be done either actively or passively. The advantage of passive is that you don't actually need injection capability and thus the Windows version of aircrack-ng can be used. The purpose of this step is to put your card into what is called monitor mode. Monitor mode is the mode whereby your card can listen to every packet in the air. As well, it will allow us to optionally deauthenticate a wireless client in a later step.
The exact procedure for enabling monitor mode varies depending on the driver you are using. To determine the driver and the correct procedure to follow , run the following command:. On a machine with a Ralink, an Atheros and a Broadcom wireless card installed, the system responds:.
The presence of a [phy0] tag at the end of the driver name is an indicator for mac, so the Broadcom card is using a mac driver.
Note that mac is supported only since aircrack-ng v1. Finally, the Ralink shows neither of these indicators, so it is using an ieee driver - see the generic instructions for setting it up. If there are any remaining athX interfaces, then stop each one. This is because the madwifi-ng drivers are being used.
In the response above, you can see that ath0 is in monitor mode, on the 2. So everything is good. For this lecture, we will refer to the router as an AP Access Point.
Once we got the Key , the sniffing process should stop and we will have an Encrypted WEP Key for authenticating in the target network. The second one is if there are no stations on the network. And the output will look something like this:. This method will wait for an ARP packet, will capture it and inject it into the traffic.
This consists of forcing the Access Point to generate a new ARP packet with a new IV , we capture this new packet and inject it into the traffic again and this has to be done until the number of packets is sufficient enough to crack the key. Before doing it you should, write a. This is another way to increase packets to a network for decrypting keys for very low traffic networks. This is a little bit hard to get it on the first try, at least for me.
Using this command:. If we split this code we will have the following actions:. But, how to forge a packet? This attack is pretty similar to the Korek Chop Chop method. You will obtain the PRGA with this command:. What does this? This tries to generate a useful packet, repeated times. Once it begins being useful, we are going the use the keystream for forging packets with the. Forging Packet same as chopchop , but with — fragment flag, for later inject the forged packet into the traffic like this:.
Both last two methods are not quite simple, you can make practices by using a multiplexer terminal in order to reproduce each step easily. The main issue in WEP is the short IV initialization vector sent as plain text, so they can be repeated, therefore by collecting a large number of IVs and with Aircrack-ng we can determine the keystream and the WEP key.
In WPA each packet is encrypted with a unique temporary key, the number of data packets that we collect is irrelevant. They do not contain information for cracking WPA keys.
Most of the packets contain useless information for cracking determining key. Authentication is done by using an 8 digit long ping not the WPA key , this means that there is a relatively small number of pin combinations, and using brute force we can guess the pin in less than 10 hours.
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