Ephemeral Identifier Security for Wireless Broadcasts
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Solution Overview
Problem
Bluetooth Smart (BLE) devices in broadcast mode lack effective security mechanisms to protect against unauthorized tracking, spoofing, and replay attacks, as the standard random MAC address mechanism is susceptible to these threats and does not provide unique device identification.
Innovation Solution
Implementing ephemeral identifiers (eIDs) that can only be resolved by authorized devices using a shared key, which expires to prevent unauthorized tracking and spoofing, and using a remote resolver to manage and update these identifiers for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random MAC addresses are used for device identification in broadcast mode, then device tracking is enabled, but security against unauthorized tracking and spoofing is compromised
Solution Approach 1:
The identifier is segmented into two parts: a stable unique identifier stored securely in the device, and a time-varying component that changes periodically. The broadcasted identifier combines both parts, allowing authorized devices with the stable identifier to track the device reliably while unauthorized devices cannot correlate broadcasts across different time periods.
Solution Approach 2:
The broadcasted identifier transitions from a static random MAC address to a dynamic identifier that changes over time according to a predictable pattern known only to authorized devices. This dynamic behavior prevents unauthorized tracking while maintaining reliable identification for authorized observers.
2Object-affected harmful factors
If MAC address rotation is implemented, then device identification is protected from static tracking, but replay attacks remain possible and unique identification is lost
Solution Approach 1:
The identifier rotation system uses feedback from a stable unique identifier stored in the device to generate subsequent broadcast identifiers. Each new identifier is derived from the stable identifier combined with a time-varying component, ensuring that rotation occurs while maintaining a cryptographic link to the unique device identity, preventing replay attacks.
Solution Approach 2:
The system changes the time-varying parameter in the identifier composition while keeping the stable unique identifier constant. This allows the broadcasted identifier to rotate over time for protection against static tracking, while the stable component ensures unique device identification and prevents replay attacks.
3Object-affected harmful factors
If ephemeral identifiers are used to prevent tracking, then unauthorized tracking is blocked, but device identification becomes unresolvable without pairing
Solution Approach 1:
The stable unique identifier is preliminarily established and stored securely in the device before broadcast operations begin. Authorized devices can use this pre-established identifier to resolve ephemeral broadcast identifiers without requiring pairing, enabling easy operation while preventing unauthorized tracking.
Solution Approach 2:
The stable unique identifier acts as an intermediary between the ephemeral broadcast identifier and the device's true identity. Authorized devices use this intermediary to resolve the ephemeral identifier to the stable identifier, enabling identification without pairing while blocking unauthorized tracking attempts.
Data Source
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AI summary
Methods and systems are provided for concealing identifying data that may be used to identify a beacon or device in broadcasts unless an observer device is able to directly or indirectly, via an authorized resolver device, translate an encrypted broadcast into the identifiable information. The wireless security scheme disclosed herein also pertains to resolving the concealed data messages to obtain the identifiable information.