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Secure Enablement and CVS without Persistent Association

Secure Enablement and CVS without Persistent Association. November 7, 2011. Authors:. Abstract.

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Secure Enablement and CVS without Persistent Association

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  1. Secure Enablement and CVS without Persistent Association November 7, 2011 Authors: S.Abraham Qualcomm Incorporated

  2. Abstract The submission provides techniques that allow a GDC dependent STA to remain enabled even if it disassociates from its GDC enabling STA. The amendment resolves an issue raised by CID 951 which highlights the need for Mode 1 APs. Due to the necessity of a secure association between a GDC dependent STA and its GDC enabling STA to obtain enablement and the requirement that an STA can have only one association, a GDC dependent STA cannot associate with a Mode 1 AP. This amendment proposes a method for a GDC Dependent STA to maintain a secure link with a GDC enabling STA while associated with another AP such as a Mode 1 AP. S. Abraham, Qualcomm Inc.

  3. Update This revision provides additional support (in the appendix) for the permissibility of Mode I APs. S. Abraham, Qualcomm Inc.

  4. Motivation • FCC rules require secure transmission of • White space map (WSM) • Contact Verification Signal (CVS) • Encrypted transmission of WSM and CVS • To comply with the above, for the current 802.11af draft a GDC dependent STA requires a continuous “secure association” to an GDC enabling AP. • 802.11 Revmb does not permit more than one association, the enabling AP will have to also provide data services • Therefore: • All APs will need to be enablers to associate dependent STAs • APs would have to be Mode II and accurate geo location capability • We present an augmentation to the current GDC enablement protocol that keeps the (GDC) Enabling AP(E-AP) function separate from the data serving AP (S-AP) S.Abraham Qualcomm Inc.

  5. Network Operation with Separate Enabler S. Abraham, Qualcomm Inc.

  6. Proposed “Augmented” Enablement Flowchart S. Abraham, Qualcomm Inc.

  7. Operation of Enablement Procedure D-STA associates with E-AP using a secure association procedure as required by the E-AP During the secure association the E-AP and D-STA generate an Enablement Key (EK) along with the PTK D-STA requests enablement from the E-AP using the enablement procedure. D-STA then disassociates from E-AP D-STA may then associate with any other AP, even other dependent APs (this AP is called the serving AP) All other communication from D-STA to E-AP use a “pull method” as described later S. Abraham, Qualcomm Inc.

  8. Obtaining a CVS from E-AP • All messages between the E-AP and D-STA (after disassociation) use self protected action frames that are encrypted using the EK generated during the association • D-STA obtains a CVS by requesting one from E-AP • CVS Request approach frees the E-AP from tracking the sleep state of the D-STA when sending the CVS • When E-AP receives a CVS request, it responds with a CVS containing the CVSIE if it is able to de-crypt the self protected action frame using the EK. • Operation when CVS indicates new WSM-ID • D-STA sends self protected Channel Availability Query( CAQ) with reason result set to WSM • D-STA uses self protected CAQ response frame to send the WSM S. Abraham, Qualcomm Inc.

  9. Frame Formats • Self protected CVS: • Similar to the CVS public action frame, with category field indicating self protected • Self protected CAQ: For WSM • Similar to CAQ public action frame with category field indicating self protected. • CVS Request: • Only contains Category and Action field S. Abraham, Qualcomm Inc.

  10. Appendix FCC Rules, Decisions, and Relevant TVBD Definitions and Terminology S. Abraham, Qualcomm Inc.

  11. A Mode I AP Is Permissible Under FCC TVWS Rules • The FCC’s main goal in the TVWS proceeding is to provide as much flexibility as possible for unlicensed uses while fully protecting the reception of broadcast TV signals. See 2008 TVWS Order at para. 54 (“we are providing for operation of personal/portable devices under two different modes: 1) controlled by a fixed device or a Mode II personal/portable device and 2) independent. In each of these cases, our goal is to make the technical requirements as simple and as reliable as possible [and] to permit a wide range of unlicensed broadband uses and applications and while ensuring that the most appropriate and effective mechanisms are in place to protect TV and other licensed services. “) • So long as a network has a single device acting in master mode – and thus protecting licensed users – it can enable any number of other devices acting as masters and clients. • See 2008 TVWS Order at para. 111 (“A network always has at least one device operating in master mode and also some devices that may be capable of operating only in client mode and some devices that may be capable of operating in either mode. All fixed TVBDs will be allowed to operate in master mode. Those personal/portable devices communicating on a master/client basis with a fixed device will be required to use channels/frequencies as directed by the fixed device. Thus, a personal/portable device operating under this arrangement will pose no more risk of interference to a licensed service than the fixed device, and because it will use less power will generally pose less risk of causing such interference.”) • See 2008 TVWS Order at para. 133 (“We envision that both the Mode I and Mode II approaches will often be incorporated into the same personal/portable device. That is, a personal/portable device could function as a master device when it is able to use geo-location/sensing and database access to identify unused TV channels in its area. If it cannot rely on these techniques but is near a fixed device or another personal/portable device that can act as a master, it could operate in client mode if it makes contact with a master station.”) • A Mode I AP is fully consistent with the FCC’s definition of a Mode I personal/portable device as well as the other definitions on the following page. S. Abraham, Qualcomm Inc.

  12. TVBD Definitions Support This Interpretation S. Abraham, Qualcomm Inc.

  13. IEEE S. Abraham, Qualcomm Inc.

  14. Part 15.202 - Certified operating frequency range • Client devices that operate in a master/client network may be certified if they have the capability of operating outside permissible Part 15 frequency bands, provided they operate on only permissible Part 15 frequencies under the control of the master device with which they communicate. Master devices marketed within the United States must be limited to operation on permissible Part 15 frequencies. Client devices that can also act as master devices must meet the requirements of a master device. For the purposes of this section, a master device is defined as a device operating in a mode in which it has the capability to transmit without receiving an enabling signal. In this mode it is able to select a channel and initiate a network by sending enabling signals to other devices. A network always has at least one device operating in master mode. A client device is defined as a device operating in a mode in which the transmissions of the device are under control of the master. A device in client mode is not able to initiate a network • Observations • Master devices send enabling signals. • Client devices are under the control of a master and cannot initiate a network. • A single device can operate as a master or a client depending on its mode of operation. • A TV band device is an unlicensed (i.e., Part 15) RF device that operates on open broadcast TV channels. See § 15.703(m). On one of the conference calls it was brought up that we need to review FCC Part 15.202, which is copied below: S. Abraham, Qualcomm Inc.

  15. KDB 594280 Restrictions on Software Configuration for devices not approved as Software Defined Radios • Many devices referred to by the Wi-Fi industry as "client devices" may not meet the definition of a Section 15.202 client, and must be approved as master devices on U.S. authorized frequencies, and must operate in accordance with the grant conditions. To qualify as a Section 15.202 client, a device cannot initiate, or be configured to initiate, any transmission including probes, beacons, or ad-hoc mode transmissions. If a device supports such network initiating functions, it shall be approved as a master device for that particular band. This includes devices that support Wi-Fi Direct modes in the bands where the device is capable of becoming a Group Owner must be approved as master devices under Section 15.202. • Observations • While it is clear that a Mode 1 AP cannot initiate the transmission of a probe or a beacon, in 802.11, no AP “initiates” the transmission of probes. The transmission of a probe is an autonomous decision at a client device (e.g., a laptop). 802.11af has very clear rules stating that any transmission (including a probe) can only be done after seeing a beacon from a Fixed or Mode 2 device. Hence we comply with the KDB. • Mode 1 APs do not initiate the transmission of a beacon autonomously. They transmit a frame (including the 802.11 beacon) only after being given permission by a Fixed or Mode 2 AP. • Also, the beacons from a Mode 1 AP do not by themselves provide permission for any other STAs to transmit. S. Abraham, Qualcomm Inc. On one of the conference calls we were asked to review KDB 594280. A relevant excerpt from that KDB is provided below:

  16. Mode 1 APs are Permitted An IEEE 802.11 AP provides access to the distribution system for associated STAs. This device may be an FCC Mode I device. This FCC Mode I device may not enable other STAs by sending control signals to them to allow them to begin transmitting in the TVWS. That must be done by a device acting as a Mode II Enabling AP. S. Abraham, Qualcomm Inc.

  17. References • Link to KDB 594280 • http://apps.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm?id=39498&switch=P S. Abraham, Qualcomm Inc.

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