FIELD

Embodiments of the present invention generally relate to the field of wireless communications. More specifically, embodiments of the present invention relate to systems and methods for measuring distances between devices using wireless and electronic communications.

BACKGROUND

There is a growing need, in the field of wireless communication, to accurately and securely determine distances (ranging) between wireless devices (e.g., wireless stations (STAs) and access points (APs)). Existing approaches to determining distances between wireless devices are vulnerable to physical-level security attacks from malicious actors, such as denial of services attacks, perturbation attacks, and spoofing attacks.

Spoofing attacks are potentially a very dangerous form of security threat when performing ranging between wireless devices. During a spoofing attack, the attacker interferes with the victim's ranging and is thereby able to control (e.g., “spoof”) the victim's perceived range. For example, some applications for wireless ranging require heightened security, such as when using wireless ranging for accessing electronic door locks, computer locks, and ATMs that provide access to funds of a bank account. In these cases, the spoofed ranging measurement should be identified as invalid and discarded to prevent property loss.

Other forms of security attacks concerning wireless ranging, such as denial of service attacks, are very difficult to protect against. In a denial of service attack, the attacker interferes with the ranging signal in such a way to prevent the AP from providing services as intended. Perturbation attacks interfere with the victims ranging, but the attacker is unable to control the resulting range as perceived by the victim.

What is needed is a technique for preventing spoofing attacks, especially in high security use cases such as electronic locks and ATMs, for example. One existing approach is to encode the long training field (LTF) sequence transmitted in a null data packet (NDP) to the AP; however, even though the LTF sequence is encoded, an attacker can use the exposed NDP as a replay attack, as depicted inFIG. 1. Therefore, more robust security measures are needed to prevent a replay attack using an exposed NDP.

SUMMARY

Method and apparatus for performing secure ranging measurements between wireless devices are disclosed herein according to embodiments of the present invention. The described embodiments use key values to indicate which LTF sequence (e.g., LTF measurement exchange) to use for performing wireless ranging measurements. A LTF sequence that is received by a wireless device that does not correspond with the associated key value is determined to be invalid. Invalid LTF sequences may be disregarded as signal noise.

According to one embodiment, a method of performing a ranging measurement using a wireless access point is disclosed. The method includes: a) transmitting a key management frame from a first wireless device, where the key management frame includes a plurality of key values and associated LTF Generation SACs; b) receiving an NDP announcement frame comprising the LTF Generation SACs from a second wireless device; c) receiving an UL-NDP frame from the second wireless device, where the UL-NDP frame includes a first LTF sequence determined according to a first key value of the plurality of key values; d) transmitting a DL-NDP frame transmitted from the first wireless device, where the DL-NDP frame includes a second LTF sequence determined according to a second key value of the plurality of key values; and e) computing ranging measurements between the first wireless device and the second wireless device using the first and second LTF sequences.

According to a second embodiment, a device for performing a ranging measurement using a wireless access point is disclosed. The device includes a memory for storing data and a processor communicatively coupled to the memory and configured to execute instructions for performing a method of ranging measurement. The method includes: a) receiving a key management frame, where the key management frame includes a plurality of key values and associated LTF Generation SACs; b) transmitting an NDP announcement frame, where the NDP announcement frame comprises the LTF Generation SACs; c) transmitting a UL-NDP frame, where the UL-NDP frame comprises a first LTF sequence determined according to a first key value of the plurality of key values; d) receiving a DL-NDP frame from a first wireless device, where the DL-NDP frame comprises a second LTF sequence corresponding to a second key value of the plurality of key values; and e) receiving a ranging measurements between the first wireless device and the second wireless device, where the ranging measurement is computed using the first and second LTF sequences.

According to another embodiment, a device for performing a ranging measurement between wireless devices is disclosed. The device includes a memory for storing data and a processor communicatively coupled to the memory and configured to execute instructions for performing a method of ranging measurement. The method includes: a) transmitting a key management frame from a first wireless device, where the key management frame includes a plurality of key values and associated LTF Generation SACs; b) receiving an NDP announcement frame comprising the LTF Generation SACs from a second wireless device; c) receiving an UL-NDP frame from the second wireless device, where the UL-NDP frame includes a first LTF sequence corresponding to a first key value of the plurality of key values; d) transmitting a DL-NDP frame transmitted from the first wireless device, where the DL-NDP frame includes a second LTF sequence corresponding to a second key value of the plurality of key values; e) authenticating that the first LTF sequence and the second LTF sequence are generated from reliable LTF Sequence Generation Information using the associated LTF Generation SACs; and f) computing ranging measurements between the first wireless device and the second wireless device using the first and second LTF sequences.

