[ISN] Increasing Wireless Security with TKIP

From: InfoSec News (isnat_private)
Date: Mon Oct 28 2002 - 04:14:10 PST

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    Forwarded from: "eric wolbrom, CISSP" <ericat_private>
    Mark Joseph Edwards
    October 23, 2002  
    What wireless security measures are on the horizon?
    The current wireless networking standards use security technology
    that's far less secure than it could be. For example, most wireless
    network administrators are familiar with the Wired Equivalent Privacy
    (WEP) protocol, which uses RC4 encryption to help protect data as it
    travels over the airwaves.
    However, researchers have proven that intruders can easily crack WEP.  
    Last year, a team of researchers published "Weakness in the Key
    Scheduling Algorithm of RC4," a paper that describes a series of
    vulnerabilities that make WEP vulnerable. In roughly the same time
    frame that the paper was published, someone posted Perl scripts on the
    Internet that helped demonstrate how vulnerabilities in WEP could be
    verified. You can read about the paper and the scripts in an editorial
    I wrote in August 2001.
    Because of the weaknesses in WEP security, several entities are
    developing stronger security technology, such as the 802.11a and
    802.11b specifications, for use with wireless network technologies.  
    If you aren't familiar with the various 802.11x network
    specifications, you can learn more about them by reading Mark Weitz's
    One up-and-coming 802.11x specification, 802.11i, is still involved in
    development and approval processes. The specification might be
    officially released by early 2003. After it's available, 802.11i will
    provide replacement technology for WEP security. Initially, 802.11i
    will provide Temporal Key Integrity Protocol (TKIP) security that you
    can add to existing hardware with a firmware upgrade. Upgraded units
    should be backward-compatible with hardware that still uses WEP.  
    Sometime later, new chip-based security that uses the stronger
    Advanced Encryption Standard (AES) protocol will replace TKIP, and the
    new chips will probably be backward-compatible with TKIP. In effect,
    TKIP is a temporary protocol for use until manufacturers implement AES
    at the hardware level.
    TKIP is a quick-fix method to quickly overcome the inherent weaknesses
    in WEP security, especially the reuse of encryption keys.  According
    to "802.11 Planet," "The TKIP [security] process begins with a 128-bit
    'temporal key,' [which is] shared among clients and access points.
    TKIP combines the temporal key with the [client machine's] MAC address
    and then adds a relatively large 16-octet initialization vector to
    produce the key that will encrypt the data.  This procedure ensures
    that each station uses different key streams to encrypt the data. TKIP
    uses RC4 to perform the encryption, which is the same as WEP. A major
    difference from WEP, however, is that TKIP changes temporal keys every
    10,000 packets. This provides a dynamic distribution method that
    significantly enhances the security of the network."
    In relation to TKIP, some companies have implemented TKIP-like
    solutions called Simple Secure Networks (SSNs), which also use an
    encryption key that changes periodically. One company, Symbol
    Technologies, currently has SSN-based products on the market. In
    addition, vendors such as Atheros Communications and Resonext
    Communications are producing chips that support WEP, TKIP, and AES
    security technologies, and wireless network gear vendors, such as
    Nokia, are already shipping hardware that's ready for TKIP security,
    waiting for the standard to be finalized.
    For a more in-depth look at wireless encryption technology, especially
    WEP and TKIP, be sure to read two articles from Intel. The first
    article discusses encryption key management in both WEP and TKIP
    protocols, and the second article discusses TKIP in considerable
    Eric Wolbrom, CISSP                     Safe Harbor Technologies
    President & CIO                         190 Goldens Bridge Ct.
    Voice 914.767.9090 ext. 6000            Katonah, NY 10536
    Fax   914.767.3911                              http://www.shtech.net
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