Cryptographic Key Custody across Factory Provisioning and Staging Deployment
Cryptographic key custody requires FIPS 140-3 HSM injection, credit-metered factory proxies, and strict scrap certificate revocation.
Append-Only Audit Log
Meaning
A cryptographic database design ensures that records can only be added sequentially and never modified or deleted once written. This append-only audit log provides a verifiable history of device firmware writes and key injections during factory assembly. The ledger relies on hash chains where each entry contains the cryptographic signature of the preceding block to prevent tampering.
Secure Ledger
Cryptographic verification blocks any unauthorized alteration of recorded production events. An append-only audit log writes every credential load to non-volatile memory with a hash of the previous transaction. Any attempt to modify a past entry breaks the chain and invalidates the entire log.
This verification runs during every secure boot to confirm the integrity of the device history before loading the operational software.
Production Tracking
Secure chips use these logs to track the state transitions of silicon during manufacturing steps. An append-only audit log records the transition from open testing state to locked production state. This prevents a compromised board from being rolled back to an unconfigured or vulnerable state.
The log resides in a protected region of flash memory that is write-once by hardware design.
Compliance Verification
Handover protocols rely on these registers to prove to buyers that each module was provisioned correctly. An append-only audit log is exported as a signed token during the final quality check to certify that the public keys on the device match the registration records. Independent auditors verify these tokens by recalculating the hash chain against the published factory keys.
This check guarantees that no unauthorized firmware was loaded during the assembly process.