How central vehicle compute platforms measure firmware stage hashes into hardware PCR registers and generate cryptographically signed Quotes before cloud backend servers authorize ignition.
Platform Configuration Registers inside a TPM cannot be directly written or overwritten; they can only be 'extended' using a cryptographic one-way hash operation: `PCR_new = SHA256(PCR_old || measurement)`. At each stage of boot, the previous stage measures the next stage before executing it. Once the vehicle is fully booted, the TPM uses its unique private Attestation Identity Key (AIK) burned into silicon to sign a Quote containing the final PCR values. The cloud backend verifies this Quote: if a single byte of the kernel was modified, the PCR values will not match, and high-voltage battery contactors remain locked open.