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This document discusses the use of PHY cooperation in wireless personal area networks (WPANs) to enhance security certification. Techniques such as reducing transmission power and incorporating ranging capability are explored. The document also highlights the need for PHY-dependent solutions and recommends referencing PHY-dependent transmission modes in the security clause.
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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: PHY Cooperation in Security Certification Date Submitted: [12 Dec 2001] Source: [Matt Welborn] Company [XtremeSpectrum] Address [8133 Leesburg Pike, Vienna, Va. 22182] Voice:[703.269.3052], FAX: [703.749.0248], E-Mail:[mattw@xtremespectrum.com] Re: [IEEE 802.15.3 Security] Abstract: Certification for Key Exchange is a concern for security. WPANs offer the ability to physically locate two devices close together to facilitate key exchange while the PHY can use a KEY EXCHANGE mode. Purpose: Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Matt Welborn, XtremeSpectrum, Inc.
The transfer of security keys in a wireless environment is always an issue. The question is “what can the PHY do in a WPAN environment to make the key transfer more secure”? • The PHY can provide a special “security” mode that takes advantage of the portability of WPAN devices. • Assuming that a WPAN device can at least once during its life be brought in close proximity to another WPAN device, the PHY could help to provide a more secure link for certification. Example techniques include: • Reduce the TX power so that the effective range is reduced to a small fraction of the nominal range. • Incorporate ranging capability so that the devices know the intervening distance (or perhaps require that devices are in the same room, e.g. no intervening walls/obstructions). • Do both #1 and #2 … this would yield an even more secure PHY mode. Matt Welborn, XtremeSpectrum, Inc.
Discussion • Doing number 1 alone can offer a increased level of security, however an attacker might still be able to defeat the mechanism from a remote location using a high gain antenna system. • Number 2 is interesting, but would be a PHY dependent solution; that is, not all PHYs would be able to support such a feature. • Number 3 is potentially the most secure but is also PHY-type dependent. Even if an eavesdropper 10 meters away with a high gain antenna can intercept the transmissions, it still could not pass a range dependent test. If the two parties exchanging certification information are using a public key system, the interception of the public keys does not weaken security. It is the ability of the user to restrict self-certification of new devices to those within a short range at a specific time that provides the added level of security in this scheme. Matt Welborn, XtremeSpectrum, Inc.
Recommended Course of Action It is recommended that the security clause contain reference to PHY-dependent transmission modes that could assist secure certification. From the security point of view, the PHY does what it can to help security certification. This may represent different actions for different PHY options, including the option of the PHY having no special security assistance mode. Matt Welborn, XtremeSpectrum, Inc.
