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1. Cryptographic Hash Functions
Can symmetric cryptography meet the requirements of the Biba model, based on the data integrity checks and proper authentication? The answer is "yes," but in a very inefficient way. Recall the practical authentication example with the UNIX (well, Linux in our case) password encryption flaw when DES in ECB is used. Of course, any of the feedback modes or 128-bit block ciphers can be used instead of DES, with the obvious performance penalties. However, in our example, MD5 scales very well. A cryptographic hash function i...

2. 802.11i Wireless Security Standard and WPA
Thus, the main hope of the international 802.11 community and network administrators lies with the 802.11i standard development. Sometimes 802.11i is referred to as the Robust Security Network (RSN) as compared to traditional security network (TSN). The "i" IEEE task group was supposed to produce a new wireless security standard that should have completely replaced legacy WEP by the end of 2003. In the meantime, some bits and pieces of the incoming 802.11i standard have been implemented by wireless equipment and software vendor...

3. Proprietary Improvements to WEP and WEP Usage
The article devoted to the proprietary and standards-based improvements for currently vulnerable 802.11 safeguards. The most publicized 802.11 vulnerability is the insecurity of WEP. We have already reviewed the cryptographic weaknesses of WEP linked to the key IV space reuse and insecure key-from-string generation algorithm. There are also well-known WEP key management issues: All symmetric cipher implementations suffer secure key distribution problems. WEP is no exception. In the original design,...

4. Penetration Testing as Your First Line of Defense
It is hard to overemphasize the importance of penetration testing in the overall information security structure and the value of viewing your network through the cracker's eyes prior to further hardening procedures. There are a variety of issues specific to penetration testing on wireless networks. First of all, the penetration tester should be very familiar with RF theory and specific RF security problems (i.e., signal leak and detectability, legal regulations pertaining to the transmitter power output, and characteris...

5. Asymmetric Cryptography
Message authentication using HMACs works just fine, but how do we distribute symmetric cipher keys among the users? We can pass them around on floppies or fancy USB pen-drives with encrypted partitions on them, but what if many users live all over the world? What if the physical key distribution method takes time and the keys must be frequently changed? This is the case with the traditional WEP, which should be rotated every few minutes. Key-encrypting keys (KEKs) were offered as symmetric cipher keys used only to encrypt...

6. Examples and Analysis of Common Wireless Attack Signatures
The best way of knowing these signatures is trying out the tools in question and sniffing out their output: "Attack through defending, defend through attacking" (Dr. Mudge). The best source on wireless network intrusion tool detection and attack signatures we are aware of is Joshua Wright's "Layer 2 Analysis of WLAN Discovery Applications for Intrusion Detection" and "Detecting Wireless LAN MAC Address Spoofing" papers. A large part of this tutorial is inspired by these brilliant articles and our experience of analyzing WLAN tr...

7. Deploying a Wireless IDS Solution for Your WLAN
How many IDS solutions that implement the recommendations and follow the guidelines we have already discussed are present on the modern wireless market? The answer is none. There are many wireless IDS solutions that look for illicit MAC addresses and ESSIDs on the monitored WLAN. Some of these solutions are even implemented as specialized hardware devices. Although something is better than nothing, in our opinion such "solutions" are a waste of both money and time. They might also give you a false sense of security. Let's...

8. Hash Functions Their Performance and HMACs
Other widely used hash functions include 128-bit MD5 from RSA Data Security, Inc., which is a very fast and commonly implemented hash. MD5 is traditionally used to encrypt Linux user passwords (hashes start with the "$1$" character), authenticate routing protocols like RIPv2 and OSPF, create checksums of binaries in RPMs, and verify the integrity of Free/OpenBSD ports files. The specifications of MD5 are available in RFC 1321. Host intrusion detection tools like Tripwire (http://www.tripwire.com) use MD5 to take snapshots of a syst...

9. Introduction to Applied Cryptography and Steganography
One can set up a reasonably secure wireless or wired network without knowing which ciphers are used and how the passwords are encrypted. This, however, is not an approach endorsed by us and discussed here. Hacking is about understanding, not blindly following instructions; pressing the buttons without knowing what goes on behind the scenes is a path that leads nowhere. Besides, security and quality of service are tightly interwoven, incorrect selection of the cipher and its implementation method can lead to a secure but sluggish...

10. Streaming Ciphers and Wireless Security
Streaming algorithms were designed to avoid speed and throughput penalties due to the implementation of block symmetric ciphers in CFB and OFB modes when bit-by-bit data encryption is required. Streaming ciphers are based on generating identical keystreams on both encrypting and decrypting sides. The plaintext is XORed with these keystreams to encrypt and decrypt data. To generate the keystream, pseudo-random generators (PRNGs) are used, thus placing stream algorithms somewhere between easy-to-break simple XORing with a predefi...