Crack Wep Encryption

Wired Equivalent Privacy (WEP) is a security algorithm for IEEE 802.11 wireless networks. Introduced as part of the original 802.11 standard ratified in 1997, its intention was to provide data confidentiality comparable to that of a traditional wired network.^[1] WEP, recognizable by its key of 10 or 26 hexadecimal digits (40 or 104 bits), was at one time widely in use and was often the first security choice presented to users by router configuration tools.^[2]^[3]

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How To Crack 128-bit Wireless Networks In 60 Seconds. Is it really true that you are able to crack 256-bit WEP encryption on a wireless network just by reading off. The TKIP encryption standard was later superseded by Advanced Encryption Standard (AES). Despite what a significant improvement WPA was over WEP, the ghost of WEP haunted WPA. TKIP, a core component of WPA, was designed to be easily rolled out via firmware upgrades onto existing WEP-enabled devices. While the underlying mechanics of WEP and WPA are very different, you’ll find that you can crack either protocol in a matter of minutes (usually) by using the aircrack-ng software on Kali. One of the key differences between our attacks is how we attack the protocol.

In 2003 the Wi-Fi Alliance announced that WEP had been superseded by Wi-Fi Protected Access (WPA).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-40 and WEP-104 have been deprecated.^[4]

WEP was the only encryption protocol available to 802.11a and 802.11b devices built before the WPA standard, which was available for 802.11g devices. However, some 802.11b devices were later provided with firmware or software updates to enable WPA, and newer devices had it built in.^[5]

5Remedies
- 5.2Implemented non-standard fixes

History[edit]

WEP was ratified as a Wi-Fi security standard in 1999. The first versions of WEP were not particularly strong, even for the time they were released, because U.S. restrictions on the export of various cryptographic technology led to manufacturers restricting their devices to only 64-bit encryption. When the restrictions were lifted, it was increased to 128-bit. Despite the introduction of 256-bit WEP, 128-bit remains one of the most common implementations.^[6]

Encryption details[edit]

WEP was included as the privacy component of the original IEEE 802.11 standard ratified in 1997.^[7]^[8] WEP uses the stream cipherRC4 for confidentiality,^[9] and the CRC-32 checksum for integrity.^[10] It was deprecated in 2004 and is documented in the current standard.^[11]

Basic WEP encryption: RC4 keystream XORed with plaintext

Standard 64-bit WEP uses a 40 bit key (also known as WEP-40), which is concatenated with a 24-bit initialization vector (IV) to form the RC4 key. At the time that the original WEP standard was drafted, the U.S. Government's export restrictions on cryptographic technology limited the key size. Once the restrictions were lifted, manufacturers of access points implemented an extended 128-bit WEP protocol using a 104-bit key size (WEP-104).

A 64-bit WEP key is usually entered as a string of 10 hexadecimal (base 16) characters (0–9 and A–F). Each character represents 4 bits, 10 digits of 4 bits each gives 40 bits; adding the 24-bit IV produces the complete 64-bit WEP key (4 bits × 10 + 24 bits IV = 64 bits of WEP key). Most devices also allow the user to enter the key as 5 ASCII characters (0–9, a–z, A–Z), each of which is turned into 8 bits using the character's byte value in ASCII (8 bits × 5 + 24 bits IV = 64 bits of WEP key); however, this restricts each byte to be a printable ASCII character, which is only a small fraction of possible byte values, greatly reducing the space of possible keys.

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 bits IV = 128 bits of WEP key). Most devices also allow the user to enter it as 13 ASCII characters (8 bits × 13 + 24 bits IV = 128 bits of WEP key).

A 152-bit and a 256-bit WEP systems are available from some vendors. As with the other WEP variants, 24 bits of that is for the IV, leaving 128 or 232 bits for actual protection. These 128 or 232 bits are typically entered as 32 or 58 hexadecimal characters (4 bits × 32 + 24 bits IV = 152 bits of WEP key, 4 bits × 58 + 24 bits IV = 256 bits of WEP key). Most devices also allow the user to enter it as 16 or 29 ASCII characters (8 bits × 16 + 24 bits IV = 152 bits of WEP key, 8 bits × 29 + 24 bits IV = 256 bits of WEP key).

Authentication[edit]

Two methods of authentication can be used with WEP: Open System authentication and Shared Key authentication.

In Open System authentication, the WLAN client does not provide its credentials to the Access Point during authentication. Any client can authenticate with the Access Point and then attempt to associate. In effect, no authentication occurs. Subsequently, WEP keys can be used for encrypting data frames. At this point, the client must have the correct keys.

In Shared Key authentication, the WEP key is used for authentication in a four-step challenge-response handshake:

The client sends an authentication request to the Access Point.
The Access Point replies with a clear-text challenge.
The client encrypts the challenge-text using the configured WEP key and sends it back in another authentication request.
The Access Point decrypts the response. If this matches the challenge text, the Access Point sends back a positive reply.

After the authentication and association, the pre-shared WEP key is also used for encrypting the data frames using RC4.

At first glance, it might seem as though Shared Key authentication is more secure than Open System authentication, since the latter offers no real authentication. However, it is quite the reverse. It is possible to derive the keystream used for the handshake by capturing the challenge frames in Shared Key authentication.^[12] Therefore, data can be more easily intercepted and decrypted with Shared Key authentication than with Open System authentication. If privacy is a primary concern, it is more advisable to use Open System authentication for WEP authentication, rather than Shared Key authentication; however, this also means that any WLAN client can connect to the AP. (Both authentication mechanisms are weak; Shared Key WEP is deprecated in favor of WPA/WPA2.)

Weak security[edit]

Because RC4 is a stream cipher, the same traffic key must never be used twice. The purpose of an IV, which is transmitted as plain text, is to prevent any repetition, but a 24-bit IV is not long enough to ensure this on a busy network. The way the IV was used also opened WEP to a related key attack. For a 24-bit IV, there is a 50% probability the same IV will repeat after 5000 packets.

In August 2001, Scott Fluhrer, Itsik Mantin, and Adi Shamir published a cryptanalysis of WEP that exploits the way the RC4 ciphers and IV are used in WEP, resulting in a passive attack that can recover the RC4 key after eavesdropping on the network. Depending on the amount of network traffic, and thus the number of packets available for inspection, a successful key recovery could take as little as one minute. If an insufficient number of packets are being sent, there are ways for an attacker to send packets on the network and thereby stimulate reply packets which can then be inspected to find the key. The attack was soon implemented, and automated tools have since been released. It is possible to perform the attack with a personal computer, off-the-shelf hardware and freely available software such as aircrack-ng to crack any WEP key in minutes.

Cam-Winget et al.^[13] surveyed a variety of shortcomings in WEP. They write 'Experiments in the field show that, with proper equipment, it is practical to eavesdrop on WEP-protected networks from distances of a mile or more from the target.' They also reported two generic weaknesses:

the use of WEP was optional, resulting in many installations never even activating it, and
by default, WEP relies on a single shared key among users, which leads to practical problems in handling compromises, which often leads to ignoring compromises.

In 2005, a group from the U.S. Federal Bureau of Investigation gave a demonstration where they cracked a WEP-protected network in 3 minutes using publicly available tools.^[14] Andreas Klein presented another analysis of the RC4 stream cipher. Klein showed that there are more correlations between the RC4 keystream and the key than the ones found by Fluhrer, Mantin and Shamir which can additionally be used to break WEP in WEP-like usage modes.

In 2006, Bittau, Handley, and Lackey showed^[2] that the 802.11 protocol itself can be used against WEP to enable earlier attacks that were previously thought impractical. After eavesdropping a single packet, an attacker can rapidly bootstrap to be able to transmit arbitrary data. The eavesdropped packet can then be decrypted one byte at a time (by transmitting about 128 packets per byte to decrypt) to discover the local network IP addresses. Finally, if the 802.11 network is connected to the Internet, the attacker can use 802.11 fragmentation to replay eavesdropped packets while crafting a new IP header onto them. The access point can then be used to decrypt these packets and relay them on to a buddy on the Internet, allowing real-time decryption of WEP traffic within a minute of eavesdropping the first packet.

In 2007, Erik Tews, Andrei Pychkine, and Ralf-Philipp Weinmann were able to extend Klein's 2005 attack and optimize it for usage against WEP. With the new attack it is possible to recover a 104-bit WEP key with probability 50% using only 40,000 captured packets. For 60,000 available data packets, the success probability is about 80% and for 85,000 data packets about 95%. Using active techniques like deauth and ARP re-injection, 40,000 packets can be captured in less than one minute under good conditions. The actual computation takes about 3 seconds and 3 MB of main memory on a Pentium-M 1.7 GHz and can additionally be optimized for devices with slower CPUs. The same attack can be used for 40-bit keys with an even higher success probability.

In 2008, Payment Card Industry (PCI) Security Standards Council's latest update of the Data Security Standard (DSS), prohibits use of the WEP as part of any credit-card processing after 30 June 2010, and prohibits any new system from being installed that uses WEP after 31 March 2009. The use of WEP contributed to the TJ Maxx parent company network invasion.^[15]

Remedies[edit]

Use of encrypted tunneling protocols (e.g. IPSec, Secure Shell) can provide secure data transmission over an insecure network. However, replacements for WEP have been developed with the goal of restoring security to the wireless network itself.

802.11i (WPA and WPA2)[edit]

The recommended solution to WEP security problems is to switch to WPA2. WPA was an intermediate solution for hardware that could not support WPA2. Both WPA and WPA2 are much more secure than WEP.^[16] To add support for WPA or WPA2, some old Wi-Fi access points might need to be replaced or have their firmware upgraded. WPA was designed as an interim software-implementable solution for WEP that could forestall immediate deployment of new hardware.^[17] However, TKIP (the basis of WPA) has reached the end of its designed lifetime, has been partially broken, and had been officially deprecated with the release of the 802.11-2012 standard.^[18]

Implemented non-standard fixes[edit]

WEP2[edit]

This stopgap enhancement to WEP was present in some of the early 802.11i drafts. It was implementable on some (not all) hardware not able to handle WPA or WPA2, and extended both the IV and the key values to 128 bits.^[19] It was hoped to eliminate the duplicate IV deficiency as well as stop brute force key attacks.

After it became clear that the overall WEP algorithm was deficient (and not just the IV and key sizes) and would require even more fixes, both the WEP2 name and original algorithm were dropped. The two extended key lengths remained in what eventually became WPA's TKIP.

WEPplus[edit]

WEPplus, also known as WEP+, is a proprietary enhancement to WEP by Agere Systems (formerly a subsidiary of Lucent Technologies) that enhances WEP security by avoiding 'weak IVs'.^[20] It is only completely effective when WEPplus is used at both ends of the wireless connection. As this cannot easily be enforced, it remains a serious limitation. It also does not necessarily prevent replay attacks, and is ineffective against later statistical attacks that do not rely on weak IVs.^[21]

Dynamic WEP[edit]

Dynamic WEP refers to the combination of 802.1x technology and the Extensible Authentication Protocol. Dynamic WEP changes WEP keys dynamically. It is a vendor-specific feature provided by several vendors such as 3Com.

The dynamic change idea made it into 802.11i as part of TKIP, but not for the actual WEP algorithm.

References[edit]

^IEEE Standard for Information Technology- Telecommunications and Information Exchange Between Systems-Local and Metropolitan Area Networks-Specific Requirements-Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. IEEE STD 802.11-1997. November 1997. pp. 1–445. doi:10.1109/IEEESTD.1997.85951. ISBN1-55937-935-9.
^ ^a^bAndrea Bittau; Mark Handley; Joshua Lackey. 'The Final Nail in WEP's Coffin'(PDF). Retrieved 2008-03-16.Cite journal requires |journal= (help)
^'Wireless Adoption Leaps Ahead, Advanced Encryption Gains Ground in the Post-WEP Era' (Press release). RSA Security. 2007-06-14. Archived from the original on 2008-02-02. Retrieved 2007-12-28.
^'What is a WEP key?'. Archived from the original on April 17, 2008. Retrieved 2008-03-11. -- See article at the Wayback Machine
^'SolutionBase: 802.11g vs. 802.11b'. techrepublic.com.
^Fitzpatrick, Jason (September 21, 2016). 'The Difference Between WEP, WPA and WAP2 Wi-Fi Passwords'. How to Geek. Retrieved November 2, 2018.
^Harwood, Mike (29 June 2009). 'Securing Wireless Networks'. CompTIA Network+ N10-004 Exam Prep. Pearson IT Certification. p. 287. ISBN978-0-7897-3795-3. Retrieved 9 July 2016. WEP is an IEEE standard introduced in 1997, designed to secure 802.11 networks.
^Walker, Jesse. 'A History of 802.11 Security'(PDF). Rutgers WINLAB. Intel Corporation. Archived from the original(PDF) on 9 July 2016. Retrieved 9 July 2016. IEEE Std 802.11-1997 (802.11a) defined Wired Equivalent Privacy (WEP).
^'WPA Part 2: Weak IV's'. informit.com. Archived from the original on 2013-05-16. Retrieved 2008-03-16.
^'An Inductive Chosen Plaintext Attack against WEP/WEP2'. cs.umd.edu. Retrieved 2008-03-16.
^IEEE 802.11i-2004: Medium Access Control (MAC) Security Enhancements(PDF). 2004. Archived from the original(PDF) on 2007-11-29. Retrieved 2007-12-18.
^Nikita Borisov, Ian Goldberg, David Wagner. 'Intercepting Mobile Communications: The Insecurity of 802.11'(PDF). Retrieved 2006-09-12.Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link)
^'SECURITY FLAWS IN 802.11 DATA LINK PROTOCOLS'(PDF). berkeley.edu.
^'Wireless Features'. www.smallnetbuilder.com.
^'T.J. Maxx data theft likely due to wireless 'wardriving''. Retrieved 2012-09-03.
^'802.11b Update: Stepping Up Your WLAN Security'. networkmagazineindia.com. Retrieved 2008-03-16.
^'WIRELESS NETWORK SECURITY'(PDF). Proxim Wireless. Retrieved 2008-03-16.Cite journal requires |journal= (help)
^'802.11mb Issues List v12'(excel). 20 Jan 2009. p. CID 98. The use of TKIP is deprecated. The TKIP algorithm is unsuitable for the purposes of this standard
^'WEP2, Credibility Zero'. starkrealities.com. Retrieved 2008-03-16.
^'Agere Systems is First to Solve Wireless LAN Wired Equivalent Privacy Security Issue; New Software Prevents Creation of Weak WEP Keys'. Business Wire. 2001-11-12. Retrieved 2008-03-16.
^See Aircrack-ng

External links[edit]

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Wired_Equivalent_Privacy&oldid=916496227'

It’s important to secure your wireless network with WPA2 encryption and a strong passphrase. But what sorts of attacks are you actually securing it against? Here’s how attackers crack encrypted wireless networks.

This isn’t a “how to crack a wireless network” guide. We’re not here to walk you through the process of compromising a network — we want you to understand how someone might compromise your network.

Spying on an Unencrypted Network

RELATED:Why You Shouldn’t Host an Open Wi-Fi Network Without a Password

First, let’s start with the least secure network possible: An open network with no encryption. Anyone can obviously connect to the network and use your Internet connection without providing a passphrase. This could put you in legal danger if they do something illegal and it’s traced back to your IP address. However, there’s another risk that’s less obvious.

When a network is unencrypted, traffic travels back and forth in plaintext. Anyone within range can use packet-capturing software that activates a laptop’s Wi-Fi hardware and captures the wireless packets from the air. This is generally known as putting the device in “promiscuous mode,” as it captures all nearby wireless traffic. The attacker could then inspect these packets and see what you’re doing online. Any HTTPS connections will be protected from this, but all HTTP traffic will be vulnerable.

Google took some heat for this when they were capturing Wi-Fi data with their Street View trucks. They captured some packets from open Wi-Fi networks, and those could contain sensitive data. Anyone within range of your network can capture this sensitive data — yet another reason to not operate an open Wi-Fi network.

Finding a Hidden Wireless Network

RELATED:Don’t Have a False Sense of Security: 5 Insecure Ways to Secure Your Wi-Fi

It’s possible to find “hidden” wireless networks with tools like Kismet, which show nearby wireless networks. The wireless network’s SSID, or name, will be displayed as blank in many of these tools.

This won’t help too much. Attackers can send a deauth frame to a device, which is the signal an access point would send if it were shutting down. The device will then attempt to connect to the network again, and it will do so using the network’s SSID. The SSID can be captured at this time. This tool isn’t even really necessary, as monitoring a network for an extended period of time will naturally result in the capture of a client attempting to connect, revealing the SSID.

This is why hiding your wireless network won’t help you. In fact, it can actually make your devices less secure because they’ll attempt to connect to the hidden Wi-Fi network at all times. An attacker nearby could see these requests and pretend to be your hidden access point, forcing your device to connect to a compromised access point.

Changing a MAC Address

Network analysis tools that capture network traffic will also show devices connected to an access point along with their MAC address, something that’s visible in the packets traveling back and forth. If a device is connected to the access point, the attacker knows that the device’s MAC address will work with the device.

The attacker can then change their Wi-Fi hardware’s MAC address to match the other computer’s MAC address. They’d wait for the client to disconnect or deauth it and force it to disconnect, then connect to the Wi-Fi network with their own device.

Cracking WEP or WPA1 Encryption

RELATED:The Difference Between WEP, WPA, and WPA2 Wi-Fi Passwords

WPA2 is the modern, secure way to encrypt your Wi-Fi. There are known attacks that can break the older WEP or WPA1 encryption (WPA1 is often referred to just as “WPA” encryption, but we use WPA1 here to emphasize that we’re talking about the older version of WPA and that WPA2 is more secure).

The encryption scheme itself is vulnerable and, with enough traffic captured, the encryption can be analyzed and broken. After monitoring an access point for about a day and capturing about a day’s worth of traffic, an attacker can run a software program that breaks the WEP encryption. WEP is fairly insecure and there are other ways to break it more quickly by tricking the access point. WPA1 is more secure, but is still vulnerable.

Exploiting WPS Vulnerabilities

RELATED:Wi-FI Protected Setup (WPS) is Insecure: Here’s Why You Should Disable It

An attacker could also break into your network by exploiting Wi-Fi Protected Setup, or WPS. With WPS, your router has an 8-digit PIN number that a device can use to connect rather than providing your encryption passphrase. The PIN is checked in two groups — first, the router checks the first four digits and tells the device if they’re right, and then the router checks the last four digits and tells the device if they’re right. There are a fairly small number of possible four-digit numbers, so an attacker can “brute force” the WPS security by trying each four-digit number until the router tells them they’ve guessed the correct one.

You can protect against this by disabling WPS. Unfortunately, some routers actually leave WPS enabled even when you disable it in their web interface. You may be safer if you have a router that doesn’t support WPS at all!

Brute-Forcing WPA2 Passphrases

How To Crack Wep Password

RELATED:Brute-Force Attacks Explained: How All Encryption is Vulnerable

Modern WPA2 encryption has to be “brute-forced” with a dictionary attack. An attacker monitors a network, capturing the handshake packets that are exchanged when a device connects to an access point. This data can be easily captured by deauthorizing a connected device. They can then attempt to run a brute-force attack, checking possible Wi-Fi passphrases and seeing if they will successfully complete the handshake.

Break Wep Encryption

For example, let’s say the passphrase is “password.” WPA2 passphrases must be between eight and 63 digits, so “password” is perfectly valid. A computer would start with a dictionary file containing many possible passphrases and try them one by one. For example, it would try “password,” “letmein,1” “opensesame,” and so on. This sort of attack is often called a “dictionary attack” because it requires a dictionary file containing many possible passwords.

Crack Wep Key

We can easily see how common or simple passwords like “password” will be guessed within a short time frame, whereas the computer may never get around to guessing a longer, less obvious passphrase like “:]C/+[[ujA+S;n9BYq9<kM5’W+fc`Z#*U}G(/W~@q>z>T@J#5E=g}uwF5?B?Xyg.” This is why it’s important to have a strong passphrase with a reasonable length.

Tools of the Trade

Weakness In Wep Encryption

If you want to see the specific tools an attacker would use, download and run Kali Linux. Kali is the successor to BackTrack, which you may have heard about. Aircrack-ng, Kismet, Wireshark, Reaver, and other network-penetration tools are all preinstalled and ready to use. These tools may take some knowledge (or Googling) to actually use, of course.

How Long To Crack Encryption

All these methods require an attacker to be within physical range of the network, of course. If you live in the middle of nowhere, you’re less at risk. If you live in an apartment building in New York City, there are quite a few people nearby who might want an insecure network they can piggy-back on.

Image Credit: Manuel Fernando Gutiérrez on Flickr

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