Subscriber Identity Module MSL Check for Spoofed OTA Messages
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Solution Overview
Problem
Existing subscriber identity modules (SIMs) are vulnerable to attacks where attackers can send spoofed OTA messages, and the current security protocols, such as IPSec based on IKE, do not effectively prevent recognition of insecure sources and protection of secret data.
Innovation Solution
A SIM that checks OTA messages for compliance with a minimum security level (MSL) by verifying the origin information using the MSL parameter, which includes data fields like TP Service Center Address, TP Originator Address, and TP Service Center Time Stamp, and forms the MSL using a cryptographic checksum to ensure only secure messages are forwarded to applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SIM card processes all incoming OTA messages, then message delivery is maximized, but security is compromised due to spoofed messages from insecure sources
Solution Approach 1:
The SIM card performs preliminary security verification by checking the MSL parameter of each incoming OTA message against the stored minimum security level before processing the message content. This preliminary action filters out insecure messages before they can compromise the system, while allowing valid messages to proceed to normal processing.
2Reliability
If the SIM card implements strict MSL verification, then security against spoofed messages is improved, but message delivery may be blocked for valid messages
Solution Approach 1:
The system uses the MSL parameter within the SPI field as a security indicator that changes based on the security level of the message. By comparing this parameter against the stored minimum security level, the SIM card can dynamically determine whether to accept or reject each message, ensuring that valid messages are delivered while blocking insecure ones.
3Reliability
If the SIM card sends cryptographically secured acknowledgment to all senders, then communication reliability is improved, but secret data may be exposed to attackers
Solution Approach 1:
The SIM card implements selective feedback by sending cryptographically secured acknowledgments only to senders whose messages pass the MSL verification. Messages that fail the security check do not receive acknowledgments, preventing attackers from using the acknowledgment mechanism to extract secret data while maintaining reliable communication with legitimate senders.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively recognizes and blocks OTA messages from insecure sources, preventing attacks by ensuring only compliant messages are processed, thereby enhancing security and protecting sensitive information.
Implementation Method 1
the MSL and the MSL parameter are formed by evaluating the first octet SPI1 of the Security Parameter Indicator SPI. According to ETSI TS 102 225 chap. 5.1.1, the data field SPI1 contains information about the security mechanisms used, such as checksums, signatures and encryption.
Data Source
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AI summary
The invention provides a subscriber identity module configured to check an incoming OTA message from a sender at the subscriber identity module for compliance with a minimum security level MSL, in that an MSL parameter of the OTA message is checked for conformity with an MSL stored in the subscriber identity module, and the OTA message is processed according to a result of the checking process. The MSL is formed using origin information which provides information about the origin of the OTA message. The MSL is formed using origin information which provides information about the origin of the OTA message.