Monotonic Counter Architecture for Replay-Resistant Vehicle Encryption
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Solution Overview
Problem
The lack of dedicated secure memory and processor in AUTOSAR-SHE compliant hardware security modules (SHE) prevents the implementation of a monotonic counter, making them vulnerable to replay attacks, which existing software solutions cannot effectively prevent.
Innovation Solution
Implementing a monotonic counter using a hardware extension with a true-random number generator (TRNG), random-access memory (RAM), and an Advanced Encryption Standard (AES) block cipher to encrypt and verify one-time passwords (OTPs), ensuring the counter value can only increase, thereby preventing replay attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a monotonic counter is implemented using software in AUTOSAR-SHE, then the device complexity is reduced and cost is lowered, but the security against replay attacks deteriorates due to lack of dedicated secure memory and processor
Solution Approach 1:
The patent segments the security function by separating the monotonic counter implementation into distinct components: a software-based counter manager that handles counter logic and a hardware-based encryption module that handles cryptographic operations. This segmentation allows the system to achieve security functionality without requiring a complete hardware security module, thus reducing device complexity while maintaining adequate security through the combined software-hardware approach.
Solution Approach 2:
The patent introduces an intermediary encryption module as a mediator between the software counter manager and the communication protocol. This intermediary component provides the necessary cryptographic protection and monotonic counter functionality without requiring the full HSM architecture, thereby reducing overall device complexity while maintaining security against replay attacks through the coordinated software-hardware system.
2Ease of manufacture
If a monotonic counter is implemented using software, then the cost is reduced compared to HSM, but the reliability of preventing counter modification and decrement deteriorates
Solution Approach 1:
The patent merges the counter management functionality with the encryption module in a coordinated software-hardware system. The software counter manager maintains the monotonic counter logic while the hardware encryption module provides secure cryptographic operations. This merging approach ensures that the counter value integrity is maintained through the combined system's collaborative operation, achieving both cost reduction and reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the encryption module receives counter values from the software manager and returns encrypted responses that include cryptographic proofs of monotonicity. This feedback loop ensures that the counter value integrity is maintained by continuously verifying that counter values are indeed increasing and have not been modified, thereby achieving reliability at lower cost.
3Device complexity
If AUTOSAR-SHE is used instead of HSM, then the device complexity and cost are reduced, but the capability to support monotonic counter deteriorates
Solution Approach 1:
The patent makes the AUTOSAR-SHE device universal by implementing a multi-functional system where the software counter manager can operate with different encryption modules. The system is designed to provide monotonic counter capability through software coordination with the hardware encryption module, enabling AUTOSAR-SHE to fulfill roles traditionally requiring HSM, thus achieving both reduced complexity and maintained capability.
Solution Approach 2:
The patent changes the operational parameters of the system by transitioning from pure hardware-based monotonic counters to a software-hybrid approach. By changing the implementation paradigm and utilizing the flexibility of software coordination with hardware encryption, the system achieves monotonic counter capability in AUTOSAR-SHE, thereby maintaining adaptability while reducing device complexity.
Data Source
AI summary
A system configured to encrypt vehicle communication includes a hardware extension that includes a true-random number generator (TRNG) configured to output a true-random number, a random-access memory configured to store the true-random number as a one-time password and a counter value received from a counter, and control logic configured to send the one-time password to an advanced encryption standard (AES) block cipher configured to encrypt the one-time password with the counter value to generate a signature, a controller in communication with the hardware extension, the controller configured to receive, the signature, store the signature at a memory, and increase the counter value at the counter to establish a second counter value.