ASIC Key Table Access Control for Reverse Engineering Protection
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Solution Overview
Problem
Existing integrated circuits, such as ASICs and ASSPs, face challenges in securing algorithms and software from reverse engineering, especially when using external RAM or ROM storage, which can be tampered with, and require encryption to prevent copying and enable selective licensing, while also needing to be cost-effective and compact.
Innovation Solution
Incorporating a non-volatile store with a key table and an initialization program that reads a key index to decrypt data on-chip, using a symmetrical encryption algorithm to strengthen security and reduce hardware costs, allowing multiple product manufacturers to use the same ASIC with encrypted data stored externally, and limiting access to the key table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If algorithms and software are stored in external RAM or ROM, then ASIC size can be kept small, but security against reverse engineering deteriorates
Solution Approach 1:
The patent introduces an intermediary decryption mechanism where encrypted algorithms are stored externally and decrypted on-chip using a key stored in a protected key table. This intermediary decryption process allows the ASIC to execute algorithms securely without storing them in plaintext, thus maintaining small size while improving security against reverse engineering.
2Adaptability or versatility
If multiple fixed keys are included in a key table to support multiple product manufacturers, then adaptability improves, but key management complexity increases
Solution Approach 1:
The patent segments the key management system into distinct key slots in the key table, where each slot can store a separate decryption key for different product manufacturers. This segmentation allows multiple clients to use the same ASIC with their own encrypted algorithms, improving adaptability while keeping key management organized and manageable through structured storage.
3Reliability
If programmable non-volatile memory is used, then security improves, but chip size and production cost increase
Solution Approach 1:
The patent extracts the non-volatile memory requirement from the ASIC chip itself and relocates it to external storage media. The key table on-chip uses smaller, faster memory while encrypted algorithms are stored externally in non-volatile memory. This extraction maintains security through encryption while reducing chip size and production costs by eliminating the need for large on-chip non-volatile memory.
Data Source
AI summary
An ASIC or ASSP has processor circuitry (110), a predetermined initialization program (100) for execution by the processor circuitry at power up, and a non-volatile key table (120) readable by the initialization program, and not accessible otherwise by the processor circuitry. The initialization program reads a key index associated with encrypted data, from external memory, and uses the key index to read a corresponding key from the table, to decrypt the encrypted data for use by the processor circuitry. Optionally another key is first decrypted and used for the decryption of the encrypted data. By keeping the key on board the chip and restricting access in this way, the key and therefore the encrypted data can be protected from software based reverse engineering. This means the encrypted data can cheaper memory chips or other storage. Thus the processor circuitry can be formed on a smaller integrated circuit.