Mutable Attestation or Measurement Reporting Data

In secure boot implementations, a System-on-Chip (SoC) typically verifies and measures each piece of code it loads during startup. This measurement is created by calculating a cryptographic hash of the code and combining it with previous measurements, building a verifiable chain of trust. The final hash value, stored in dedicated hardware registers, should provide an unforgeable record of everything that executed. However, if these measurement registers are not properly protected, they become the weak link in the chain. When an adversary can directly modify these register contents, they can replace the legitimate measurement with a fake value that matches their malicious code. This allows them to spoof attestation reports and verification checks, making a compromised device appear trustworthy. The core issue is that the hardware provides mutable storage for what should be immutable evidence, breaking the fundamental security guarantee of measured boot.