Composite Customer ID for Chipset Certificate Revocation
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Solution Overview
Problem
Current methods for managing customer public key revocation in chipsets are inefficient, as revoking one customer's key requires re-certifying all others, complicating manufacturing and inventory control, especially when multiple customers use the same chipset type.
Innovation Solution
A composite customer ID (CCID) is stored in one-time-programmable memory, allowing individual OTP CIDs to be managed for each customer, enabling revocation of specific certificates without affecting others, using a multi-bit CCID with customer-specific index positions and version numbers for flexible certificate management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single verification number is used for all customers in chipset OTP, then revocation of one customer's key is possible, but all other customer certificates become invalid requiring re-certification
Solution Approach 1:
The patent segments the verification mechanism by allocating a unique verification number to each customer. The chipset OTP contains a verification number that is compared against verification numbers in customer public key certificates. This segmentation allows individual customer certificates to be revoked by simply removing or invalidating that customer's verification number from the OTP, without affecting other customers' certificates. The verification process is divided into customer-specific units rather than using a single collective verification mechanism.
2Reliability
If different verification numbers are provisioned for each customer in chipset OTP, then individual certificate revocation is enabled, but manufacturing and inventory control become more difficult
Solution Approach 1:
The patent applies preliminary action by pre-provisioning each chipset OTP with a verification number during manufacturing, before the chipset is delivered to the customer. This verification number is stored in the OTP memory along with other chipset identification data. By having the verification number already in place before deployment, the system enables later individual certificate revocation without requiring complex runtime provisioning or reconfiguration. The manufacturing process incorporates the verification number assignment as a preliminary step, simplifying later operational control.
3Quantity of substance
If a customer public key is stored in SW Boot, then OTP memory is saved, but an extra hash verification step is required before SW Boot execution
Solution Approach 1:
The patent extracts the customer public key from the OTP memory and stores it in the SW Boot instead. Only the cryptographic hash of the customer public key is retained in the OTP memory for verification purposes. During boot, the chipset computes the hash of the customer public key extracted from SW Boot and compares it against the stored hash in OTP. This extraction approach significantly reduces OTP memory consumption while maintaining security through the hash verification mechanism.
4Reliability
If integrity checks are performed before customer public key provisioning, then counterfeit protection is enabled, but the verification process becomes more complex
Solution Approach 1:
The patent performs integrity checks as a preliminary action before the customer public key is provisioned in OTP. The chipset firmware verifies the integrity of the SW Boot and the customer public key using a root key embedded in the firmware, before allowing execution. This preliminary verification ensures that even if the OTP has not been programmed with the final customer public key, the system can still authenticate legitimate SW Boot and protect against counterfeit chipsets. The integrity check is performed upfront rather than requiring the OTP to be pre-provisioned.
Data Source
AI summary
A composite customer ID (CCID) is stored in the OTP memory of integrated circuit chipsets used by a number of different customers. The CCID includes individual customer IDs (CIDs) at defined index positions, each corresponding to a different customer. Each chipset allows or disallows software booting, based reading a certificate index value from a given customer's certificate, reading an OTP CID from OTP, as pointed to the by certificate index value, and evaluating the OTP CID with a certificate CID read from the certificate. Thus, while CCID carries information for a plurality of customers, each customer's certificate points only to that customer's OTP CID, which can be changed to revoke that customer's certificate without revoking the other customers' certificates. The CCID also may include a version number, where the chipsets allow or disallow software booting based on evaluating the certificate version number in view of the CCID version number.