Dynamic Memory Scrambler for DDR Security
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Solution Overview
Problem
Existing memory data scrambling systems in DDR interfaces use static encryption methods, making them vulnerable to attacks and cryptanalysis, as once a scrambling method is selected, it is consistently applied, offering little security against external observation.
Innovation Solution
A dynamic memory data scrambling system that includes a scrambler, descrambler, key generator, and scrambler selection table within an integrated circuit, allowing for real-time key changes and algorithm selection, enabling dynamic rescrambling of memory contents without performance degradation by integrating with the DDR refresh process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static scrambling method is selected for DDR memory, then the system is simpler to implement and maintain, but the security against attacks and cryptanalysis deteriorates
Solution Approach 1:
The patent implements dynamic key selection where the scrambler can switch between multiple scrambling keys based on a selection table. The key generator produces multiple keys and the system dynamically changes which key is applied to different memory regions or at different times, transforming the static scrambling approach into a dynamic one that adapts to security requirements while maintaining manageable complexity through structured key management
Solution Approach 2:
The system changes the scrambling parameter (key) dynamically rather than keeping it fixed. The key generator creates multiple scrambling keys and the selection table determines which key to use, allowing the scrambling behavior to change based on parameters such as memory region, time, or security requirements, thereby improving security without requiring a complete redesign of the scrambling mechanism
2Reliability
If dynamic rescrambling is implemented while the system is in operation, then security against cryptanalysis is improved, but the system complexity and operational overhead increase
Solution Approach 1:
The key generator produces multiple scrambling keys in advance and stores them in a selection table before they are needed. This preliminary preparation of keys allows the system to perform dynamic key switching during operation without the overhead of generating keys in real-time, simplifying the operational complexity while maintaining the security benefits of dynamic rescrambling
Solution Approach 2:
The selection table acts as an intermediary between the key generator and the scrambler. It pre-organizes which keys should be used in different scenarios or time periods, allowing the scrambler to simply look up and use the appropriate key without complex decision-making logic, thereby easing operational complexity while enabling dynamic key changes
3Object-affected harmful factors
If multiple scrambling keys are used dynamically, then the resistance to attacks and cryptanalysis is enhanced, but the key management complexity increases
Solution Approach 1:
The key management system is segmented into distinct functional components: a key generator that produces keys, a selection table that organizes and selects keys, and the scrambler that applies them. This segmentation allows each component to handle a specific aspect of key management independently, reducing overall complexity while enabling the use of multiple keys for enhanced attack resistance
Data Source
AI summary
A memory data scrambling system that can dynamically rescramble the contents of a memory while the system is in operation includes an application-specific integrated circuit (ASIC) that has an ASIC bus fabric, a double data rate (DDR) memory controller coupled to the ASIC bus fabric, a dynamic memory scrambler coupled to the DDR memory controller, the dynamic memory scrambler comprising a scrambler, a descrambler, a scrambler selection table, and a key generator and a DDR PHY coupled to the dynamic memory scrambler. The DDR PHY is coupled to an external DDR memory external to the ASIC. The dynamic memory scrambler includes a refresh timer that, upon expiration, causes data in a region of the DDR to be read, descrambled, rescrambled using a different scrambling key, and stored back into the region of the DDR in place of a DDR refresh.