UEFI Firmware Authenticated Variable Hash Verification
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Solution Overview
Problem
UEFI-compliant computing devices face challenges in detecting and protecting against physical attacks that modify Authenticated Variables stored in ROM areas, as existing signature checking mechanisms are ineffective against direct physical modifications.
Innovation Solution
A firmware-based mechanism that creates and stores a hash of Authenticated Variables' contents in a non-volatile location, allowing for comparison of hashes to detect unauthorized modifications, and optionally utilizes a Trusted Platform Module (TPM) for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signature checking is implemented to protect software and drivers, then software authenticity is improved, but physical attacks on Authenticated Variables in ROM can still modify security data undetected
Solution Approach 1:
The patent applies preliminary action by creating a hash of the Authenticated Variables and storing it in a protected location before any potential attacks can occur. This pre-computed hash serves as a baseline for future comparison, enabling detection of any subsequent modifications to the Authenticated Variables in the security database.
Solution Approach 2:
The patent introduces a hash function as an intermediary mechanism that transforms the Authenticated Variables into a comparable format. This hash acts as a mediator between the security data and the verification process, allowing indirect but effective detection of physical attacks without directly exposing the sensitive Authenticated Variables.
2Stability of the object's composition
If Authenticated Variables are protected from alteration, then security data integrity is improved, but detection of physical modifications to ROM areas becomes difficult
Solution Approach 1:
The patent creates a copy of the Authenticated Variables in the form of a hash value and stores it in a protected location. This copy serves as a reference that can be compared against future states of the Authenticated Variables, enabling detection of physical modifications without directly compromising the original security data in ROM.
Solution Approach 2:
The patent replaces direct monitoring of physical ROM modifications with a computational approach using hash functions. Instead of attempting to physically detect or prevent ROM alterations, the system uses cryptographic hashing to create a detectable signature of the Authenticated Variables, substituting mechanical/physical protection with mathematical verification.
3Measurement precision
If hash comparison mechanism is implemented to detect modifications, then detection capability is improved, but system complexity increases
Solution Approach 1:
The patent changes the parameter representation of the Authenticated Variables by transforming them into hash values. This parameter transformation enables precise detection of modifications while keeping the implementation relatively simple, as hash functions are well-established cryptographic primitives that can be efficiently implemented in firmware without requiring complex additional hardware or software infrastructure.
Data Source
AI summary
A firmware-based mechanism for protecting against physical attacks on ROM areas holding Authenticated Variables. A first hash of contents of at least one Authenticated Variable is created by a computing device's UEFI-compliant firmware and stored in a non-volatile storage location. Subsequently a second hash of contents of the at least one Authenticated Variable is created by the firmware and compared by the firmware to the stored hash to identify unauthorized modifications of the at least one Authenticated Variable occurring after the creation of the first hash.