Multilevel Memory Cell Security via Validity States
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Solution Overview
Problem
Existing methods for securing data in non-volatile memory of portable data carriers, such as chip cards, are inadequate as they require time-consuming checksum calculations and are insufficient in protecting against tampering attacks, especially when the complete memory is not adequately protected.
Innovation Solution
The method involves selectively defining the levels of multilevel memory cells as valid or invalid based on a required security level, allowing for scalable security by varying the ratio of valid to invalid levels, and dynamically defining these levels using a table or pseudo-random number generator to enhance protection against tampering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If checksums are calculated and stored for complete memory protection, then security against tampering is improved, but time consumption increases and device complexity increases
Solution Approach 1:
The memory is divided into multiple protection areas, each with its own checksum. Instead of calculating one checksum for the entire memory, separate checksums are maintained for different memory segments, reducing the computational burden while maintaining security for each protected area.
Solution Approach 2:
Different memory areas are protected with different levels of checksum protection based on their sensitivity. Critical areas have checksum protection while less critical areas may not require it, allowing selective protection that reduces overall time consumption while maintaining security where needed.
2Reliability
If multiple checksums are used for different memory areas, then security coverage is improved, but device complexity increases
Solution Approach 1:
The memory is segmented into protection areas, with each area having its own checksum. This segmentation allows systematic management of multiple checksums through a structured approach, reducing the complexity of tracking and managing security across the entire memory space.
3Quantity of substance
If all memory levels are used for data storage, then storage capacity is improved, but security against tampering deteriorates
Solution Approach 1:
Different levels of the same memory cell are assigned different validity statuses based on security requirements. Some levels are marked as valid for data storage while others are marked as invalid, allowing the system to maintain security by rejecting tampered data regardless of which level was modified.
4Reliability
If the complete memory is protected with checksums, then security is improved, but productivity decreases
Solution Approach 1:
Not all memory areas require checksum protection. The system identifies which memory areas need security and applies checksums only to those specific areas, allowing faster writing operations in unprotected areas while maintaining security where required.
Data Source
AI summary
A method for securely storing data in a multilevel memory of a portable data carrier. The multilevel memory includes one or several multilevel memory cells (SZ) which can assume respectively at least three levels (E, NE). The at least three levels represent a different data content, regarding which respective levels (E, NE) of a memory cell (SZ) are defined as valid or invalid. The levels (E, NE) of a respective memory cell (SZ) are selectively defined as valid or invalid in dependence on a required security level.