Secure Sidelink Positioning via Cryptographic PRS Encoding
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Solution Overview
Problem
Wireless communication systems, particularly in sidelink positioning, are vulnerable to attacks where an attacker can predict positioning reference signals (PRS) and replicate them, compromising the security of positioning information exchanged between user equipment (UEs).
Innovation Solution
Implementing cryptographic key-based security measures, where an initiator UE transmits a session key to a target UE, which selects and encodes a PRS sequence using this key, ensuring secure transmission and reception of PRS messages, including encoding with a nonce and using UE-specific keys for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PRS sequences are transmitted without cryptographic encoding, then positioning procedures can be performed with simpler processing, but the system becomes vulnerable to attacks where attackers can predict and replicate PRS signals
Solution Approach 1:
The patent applies parameter changes by transforming the PRS sequence from a predictable pattern to a cryptographically encoded sequence using session keys and nonces. The encoding process changes the parameters of the PRS signal by applying cryptographic functions (e.g., AES encryption) to the base PRS sequence, making it unpredictable to attackers while maintaining its positioning functionality for authorized UEs.
Solution Approach 2:
The patent introduces cryptographic intermediaries (session keys and nonces) that mediate between the positioning function and security requirements. These intermediaries act as a layer between the PRS sequence generation and transmission, enabling secure communication without fundamentally changing the underlying positioning mechanism. The session key serves as an intermediary that both transmitting and receiving UEs use to encode/decode PRS sequences.
2Reliability
If cryptographic encoding is applied to PRS sequences, then security against prediction and replication attacks is improved, but the processing complexity at transmitting and receiving UEs increases
Solution Approach 1:
The patent applies preliminary action by performing cryptographic encoding of the PRS sequence before transmission. The transmitting UE encodes the base PRS sequence with the session key and nonce in advance, creating a secure PRS sequence that is then transmitted. This preliminary encoding step ensures security is built into the transmission process itself, rather than requiring complex verification at reception.
Solution Approach 2:
The patent implements self-service through symmetric cryptographic encoding where the same session key is used by both transmitting and receiving UEs for encoding and decoding operations. Each UE independently performs the encoding/decoding using its stored session key and the received nonce, without requiring assistance from network entities or additional cryptographic infrastructure during the actual positioning exchange.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A target user equipment (UE) may receive an indication of a session key from an initiator UE in a sidelink communications system, from a network entity (e.g., a base station), or the like. In some cases, the target UE may also receive an indication of a nonce in a message of a PRS procedure. The target UE may select a positioning reference signal (PRS) sequence for the PRS procedure using the session key and optionally the nonce, such as by using a defined function at the target UE with the session key and the nonce as an input. Once the target UE selects the PRS sequence, the target UE may encode the PRS sequence and may transmit the PRS sequence to the initiator UE.