OTA Message Deciphering Counter Field Validation
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Solution Overview
Problem
Existing methods for detecting Over The Air (OTA) messages affected by errors, particularly cryptographic errors, fail to distinguish between ciphering errors and other types of errors, potentially compromising security by providing information that can be used to retrieve the cryptographic key, especially in the absence of optional checksum, digital signature, or redundancy checks.
Innovation Solution
A method that involves receiving and deciphering OTA messages, reading the counter field (PCNTR) and padding bytes, and detecting incongruent values to identify incorrect ciphering, which may involve specific intervals for cryptographic algorithms like DES or AES, to prevent information leakage and implement countermeasures against hacker attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If generic error response is returned for OTA message errors, then communication simplicity is maintained, but security is compromised due to information leakage that can reveal cryptographic keys
Solution Approach 1:
Instead of returning generic error messages that leak information, the system inverts the approach by returning specific error codes that indicate cryptographic failures without revealing key information. This distinguishes cryptographic errors from transmission errors while maintaining security.
Solution Approach 2:
The error response parameter is changed from generic messages to specific error codes with different values. This allows the receiving device to communicate failure types without providing useful information for key recovery attacks.
2Reliability
If optional control modes (Cryptographic Checksum, Digital Signature, Redundancy Check) are used, then message integrity and authenticity are verified, but device complexity and processing overhead increase
Solution Approach 1:
Instead of implementing all three control modes (Cryptographic Checksum, Digital Signature, Redundancy Check), the patent applies a partial approach by using only the counter field validation method. This provides sufficient security for detecting cryptographic errors without the full complexity of multiple control modes.
3Productivity
If OTA messages are transmitted without optional control modes to accelerate communication, then communication speed is improved, but the ability to detect cryptographic errors is reduced
Solution Approach 1:
The counter field is validated immediately after message reception, before any further processing. This preliminary validation quickly detects cryptographic errors without requiring additional control modes or slowing down the communication flow.
Data Source
AI summary
A method is to detect a message compatible with the OTA (Over The Air) standard and affected by a wrong ciphering. The method may include receiving the ciphered OTA message; deciphering the OTA message; and reading a counter field of padding bytes in the deciphered OTA message and reading corresponding padding bytes in the OTA message deciphered. The method may also include detecting at least one bit in at least one of the padding bytes of the OTA message deciphered, with the at least one bit being indicative of the wrong ciphering.