Anti-Rollback Protection

The core enforcement mechanism of anti-rollback. A monotonic counter is a hardware register that can only be incremented, never decremented. Each firmware update carries a security version number (SVN). During boot, the hardware compares the firmware's SVN against the counter value. If the firmware's SVN is lower, the boot process is halted.

• Storage: Typically stored in One-Time Programmable (OTP) memory or a replay-protected partition.
• Mechanism: The counter is incremented only after a new firmware's signature is successfully verified.
• Result: An attacker cannot load an older, vulnerable firmware even with physical access.

The foundational hardware component that provides immutable cryptographic functions and secure storage. It serves as the first link in a system's chain of trust, verifying firmware and software integrity before any other code executes.

• Immutable Storage: Stores the monotonic version counter used for anti-rollback checks.
• First Instruction: The HRoT is the first code to run, ensuring the anti-rollback check cannot be bypassed by compromised software.
• Cryptographic Anchor: Provides the trusted key material to verify firmware signatures before comparing versions.

A cryptographically enforced process for delivering and installing new firmware images. This mechanism ensures the authenticity, integrity, and freshness of the update package.

• Version Check: The update process queries the hardware-stored version counter before installation.
• Atomic Operation: The version counter is only incremented after a successful, fully verified update to prevent bricking.
• Signed Metadata: The firmware package includes a signed manifest containing the target version number, which is compared against the current counter.

A secured, authenticated data partition in eMMC or UFS storage that guarantees data integrity and prevents replay attacks. It uses a shared secret key and a write counter to validate operations.

• Hardware Counter: The RPMB's internal write counter is a physical implementation of an anti-rollback mechanism.
• Authenticated Reads: The host must prove knowledge of the shared secret to read the counter, preventing a compromised OS from spoofing the version.
• Non-Volatile Storage: The counter persists across power cycles, ensuring the rollback protection is durable.

A security capability, guided by NIST SP 800-193, that protects platform firmware and critical data against unauthorized modification, detects corruption, and recovers to a known good state.

• Protection: Ensures the anti-rollback counter itself cannot be modified by unauthorized entities.
• Detection: Cryptographically verifies the integrity of the firmware and its version metadata before boot.
• Recovery: If a rollback attack is detected, the system automatically restores the last known good, authenticated firmware image.

A hierarchical security model where each stage of the boot process cryptographically validates the integrity and authenticity of the next stage before execution. It is anchored by an immutable Hardware Root of Trust.

• Transitive Verification: The HRoT verifies the bootloader, which verifies the OS, ensuring the anti-rollback check is enforced at the earliest possible stage.
• Measurement vs. Enforcement: The chain can be designed to simply measure (log) or actively enforce (halt) if a version mismatch is found.
• Broken Chain: If any link fails to verify, including an anti-rollback check, the boot process is halted, preventing the system from reaching a vulnerable state.

A hardware security standard that layers boot states to create a compound device identity. It enables secure boot and remote attestation without requiring a discrete TPM.

• Layered Identity: Each firmware layer's identity is cryptographically combined with the previous layer's secret. A rollback to an older layer would produce a different, invalid compound identity.
• Implicit Anti-Rollback: Because the device's unique identity changes with each firmware version, a rolled-back device cannot impersonate the current, trusted version to a remote server.
• Remote Verification: A remote attestation server can detect a rollback by observing a change in the device's compound identity.