Session Key Segmentation for Secure IoT Ranging
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Solution Overview
Problem
RF ranging systems face challenges in maximizing security and link budget while minimizing current consumption, latency, and system cost, particularly in low-power Internet-of-Things (IoT) technologies and automotive passive key-less entry systems.
Innovation Solution
The implementation of a communication system where communication devices use a security-sequence-counter-value that is continuously updated and encrypted, with derived session keys generated using a key derivation function, to ensure secure communication and prevent third-party tracking, utilizing Bluetooth or IR-UWB for key synchronization and data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encryption keys are frequently updated to enhance security, then security is improved, but current consumption and system complexity increase
Solution Approach 1:
The patent segments the encryption key into two parts: a long-term master key stored securely in hardware, and a short-term session key used for actual encryption. This segmentation allows frequent session key updates without repeatedly accessing the master key, reducing power consumption while maintaining security.
Solution Approach 2:
The patent performs preliminary key derivation offline, storing multiple pre-computed session keys in memory. During active communication, these pre-computed keys are used without requiring real-time cryptographic operations, significantly reducing current consumption during frequent key updates.
2Reliability
If different session keys are used for each frame to prevent tracking, then privacy protection is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent divides the key management into hierarchical levels: a stable master key for identity, and multiple ephemeral session keys for different frame types. This segmentation enables privacy protection through frequent key changes while simplifying processing by reusing the same derivation function across different key levels.
Solution Approach 2:
The patent changes the temporal parameter of key usage by introducing frame-type-specific session keys with different validities. Each frame type (e.g., ranging frames, data frames) uses a dedicated session key that is valid only for that specific frame type, providing privacy without requiring complete key re-generation for every single frame.
3Reliability
If multiple derived session keys are generated for different frame types, then security against side-channel attacks is improved, but key management complexity increases
Solution Approach 1:
The patent segments encryption keys by frame type, creating distinct session keys for different communication purposes (ranging, data transfer, acknowledgment). This segmentation prevents side-channel attacks that exploit patterns in encryption operations while maintaining manageable key complexity through a systematic key derivation hierarchy.
Solution Approach 2:
The patent implements a universal key derivation function that can generate multiple types of session keys from a single master key. This multi-functional approach simplifies key management by providing a single entry point for key generation while supporting diverse encryption needs across different frame types.
4Reliability
If key validity counters are maintained and synchronized between devices, then security is improved, but communication latency increases
Solution Approach 1:
The patent performs preliminary key synchronization during connection establishment, pre-aligning the key validity counters between devices. This preliminary action eliminates the need for frequent counter synchronization during active communication, reducing latency while maintaining security through pre-established key validity tracking.
Data Source
AI summary
A method for operating system to transmit a plurality of frames from a first communication device to a second communication device is disclosed. The method incudes generating a security-sequence using a security-sequence-counter-value, changing the security-sequence-counter-value to a new security-sequence-counter-value; encrypting, at the first communication device, the security-sequence using a first-derived-session-key to provide an encrypted-security-sequence-counter-value; providing, at the first communication device, a frame comprising the security-sequence and encrypted-security-sequence-counter-value, transmitting a first-type frame from the first communication device to the second communication device, decrypting the encrypted-security-sequence-counter-value using the first-derived-session-key to provide the security-sequence-counter-value, configuring a security-sequence detector to detect a security-sequence using the security-sequence-counter-value, setting a key-validity-counter-value in accordance with the number of first-type frames transmitted since the first-derived-session-key was updated; and updating the first-derived-session-key based on a master-session-key in response to the key-validity-counter-value reaching an update value.