Wireless Device Anti-Tracking via Dynamic Hashed Counters
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Solution Overview
Problem
Conventional wireless systems, such as Bluetooth and WiFi Aware networks, are vulnerable to tracking through replay attacks due to their reliance on static identity keys and lack of anti-tracking mechanisms.
Innovation Solution
Implementing a method that establishes a wireless encrypted connection using long-term encryption keys (LTKs) and anti-tracking (A-T) count values, where a hashed anti-tracking counter (HATC) is generated by hashing the LTK and a changed A-T count value, and only authenticating communications with peers possessing a valid HATC, thereby preventing unauthorized responses and tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If devices use static identity keys (RPAs, NIR tags) for peer identification, then device identification and connection establishment are simplified, but devices become vulnerable to tracking through replay attacks
Solution Approach 1:
The patent transforms static identity keys into dynamic identifiers by incorporating a counter value that changes with each communication session. The identity value is generated by hashing the long-term encryption key with a dynamic counter, ensuring that while the device can be identified, the identifier changes over time preventing replay attacks and tracking.
Solution Approach 2:
The patent changes the parameter of identity from static to dynamic by introducing a counter value that increments with each session. This parameter change allows the same device to present different identity values in different sessions, maintaining identifiability while preventing tracking through replay of old identity values.
2Speed
If devices respond to any received advertisement or identity message, then connection establishment is fast and simple, but devices can be tracked by analyzing response patterns
Solution Approach 1:
The patent applies preliminary anti-action by verifying the counter value in the received identity message against the locally stored counter before responding. This pre-verification prevents unauthorized responses to replayed messages while allowing legitimate connection requests to proceed quickly, maintaining speed while preventing tracking.
Solution Approach 2:
The patent implements feedback by comparing the received counter value with the stored counter value and only responding when they match. This feedback mechanism ensures that devices only respond to legitimate, current session requests rather than replayed messages, preventing tracking through response pattern analysis.
3Reliability
If devices authenticate every communication using full key exchange, then security is maximized, but communication overhead and processing time increase
Solution Approach 1:
The patent applies preliminary action by performing the full key exchange and authentication process once during initial device pairing, storing the long-term encryption key and counter value. Subsequent communications only require verifying the counter value and generating/hashing identity values, dramatically reducing authentication complexity while maintaining security.
Solution Approach 2:
The patent segments the authentication process into two phases: an initial full authentication phase where keys are exchanged and stored, and subsequent simplified verification phases where only counter values need to be checked. This segmentation reduces the complexity of ongoing authentication while maintaining security through the pre-established key.
Data Source
AI summary
A method can include establishing a wireless encrypted connection; establishing a long term encryption key (LTK) and an anti-tracking (A-T) count value for a peer device; storing the LTK and A-T count value in a nonvolatile memory circuit; receiving a communication that includes an identity value corresponding to the peer device and a peer hashed anti-tracking count (HATC); generating at least one local HATC by executing a predetermined hash function on at least the LTK and a changed A-T count value that varies from the stored A-T count value by a predetermined amount. The received peer HATC can be authenticated with the at least one local HATC. In response to the peer HATC being authenticated, communications can occur with the peer device. In response to the peer HATC not being authenticated, communications may not occur with the peer device. Related devices and systems are also disclosed.