AirdecapNG

Airdecap-NG is simple and easy to use tool and is a part of Aircrack-NG suite of products. Aircrack-NG is a set of tools for auditing wireless networks. These tools automate in between steps involved in WEP cracking, from setting the interface in monitor mode to sniffing packets, re-injecting packets, examining these packets against different attack vectors, cracking the WEP key and finally decrypting the WEP-encrypted packets. Airdecap-NG automates the last stop i.e. decrypting the wireless packets.

With the help of aircrack NG and other tools one can easily crack the WEP key, but the story is not complete unless one actually reads the encrypted information in clear text. Airdecap NG comes as a handy tool for this purpose. The command line inputs for this tool are input pcap file which needs to be decrypted and the encryption key in hex format. Airdecap-NG tries to decrypt every encrypted packet in the packet trace with the user provided key and stores these decrypted packets in another file in pcap file format.

Airdecap NG is capable of decrypting WPA packets as well. For decrypting WPA packets one has to provide WPA pass phrase or Pairwise Master Key in hex. If the trace contains packets from different BSSIDs which are using different keys, the BSSID command line selection can be used so that the given key will be applied for only selected packets.

This video will discuss the usage of Airdecap NG with some illustrative examples.

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Newer version on wireshark (formerly known as ethereal) also provides support for decryption of WEP keys. For more details, visit wireshark video page.

WEP uses RC4 algorithm for generating key stream. With the help of IV (Initialization Vector) and the hex key, RC4 with PRGA can obtain the key stream which when ex-or with the encrypted packet gives the decrypted packet.

Links

1. Airdecap-NG download

2. Airdecap-NG Home page

Amit Vartak, 27 is working in wired and wireless security fields since last 3-4 years. His current area of interest includes IEEE 802.11 (Wi-Fi) suite of protocols, vulnerabilities in these protocols and countermeasure for those vulnerabilities. Working on cutting edge tools and technology always keeps him busy. He has contributed from concept level to final prototyping for the presentations in Defcon 2007 (The Emperor Has No Cloak - WEP Cloaking Exposed) and Toorcon 2007 (Caffe latte attack). He holds 2 patents with USPTO (current status: Patent Pending) and a few papers in IEEE journals on wireless protocol vulnerabilities. Prior to this, he was working on MEMS (Micro Electro Mechanical Systems) and has published a few papers in SPIE and ICMAT. (Yeah… kindda orthogonal fields… but technology really doesn’t limit the talent :) He did his masters in Electrical Engineering from one of the premier institutes in India, Indian Institute of Technology, Bombay (IIT-Bombay) and his under graduation, from University of Mumbai in Electronics and Telecommunication Engineering. He is currently working with AirTight Networks Inc. as a team lead in technology group since last 3 years.You can get in touch with him at amitcv[at]gmail[dot]com