State Permutation Logic Locking for Sequential Circuit Security
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Solution Overview
Problem
Existing methods for securing sequential circuits are inadequate, as they are vulnerable to reverse engineering and side-channel attacks, particularly since conventional logic locking techniques focus on combinational logic and are implemented at the gate netlist level, making them prone to attacks that exploit power and timing patterns.
Innovation Solution
The State Permutation Logic Locking (SPeLL) method encrypts the state encodings of sequential circuits at the Register-Transfer Level (RTL) using a cryptographic key, scrambling the state transitions into a random permutation, which is difficult to determine, thus providing immunity to reverse engineering and side-channel attacks without adding dummy states or modifying hardware devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional logic locking techniques are applied to combinational logic, then protection against overproduction and reverse engineering is improved, but sequential circuits remain vulnerable to side-channel attacks and power analysis
Solution Approach 1:
The patent divides the protection approach into two distinct segments: (1) conventional logic locking for combinational logic protection, and (2) state encoding permutation for sequential circuit protection. This segmentation allows each segment to address specific threats independently, with the first segment handling overproduction and reverse engineering, while the second segment specifically counters side-channel attacks and power analysis by randomizing state transition patterns
Solution Approach 2:
The patent creates a composite protection mechanism by combining conventional logic locking techniques with state encoding permutation. This composite approach integrates two different protection methodologies - the key-based logic locking and the state permutation scheme - to provide comprehensive security that addresses both combinational and sequential circuit vulnerabilities simultaneously
2Object-affected harmful factors
If state encoding permutation is applied to sequential circuits, then immunity to side-channel attacks is improved, but the complexity of determining correct state transitions increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the permutation mapping between original state encodings and permuted state encodings in a lookup table during the design phase. This preliminary preparation ensures that during runtime, the circuit can efficiently apply the permutation without complex real-time computation, thus achieving side-channel immunity while maintaining operational efficiency
Solution Approach 2:
The patent introduces an intermediary permutation layer that sits between the original state encoding and the actual state representation. This intermediary mapping acts as a mediator that obscures the relationship between consecutive state values, preventing direct inference of transition patterns while maintaining the functional correctness of the sequential circuit through the use of permutation lookup tables
3Reliability
If multiple protection techniques are combined, then overall security is improved, but hardware overhead and implementation complexity increase
Solution Approach 1:
The patent merges the logic locking mechanism and state encoding permutation into a unified protection framework. By combining these two techniques, the system achieves comprehensive security where the logic locking protects the combinational logic and the state permutation protects the sequential elements, while sharing common cryptographic key infrastructure to reduce overall hardware overhead
Solution Approach 2:
The patent creates a universal protection architecture that can be applied to both combinational and sequential circuits using the same cryptographic key. The state permutation mechanism serves multiple functions: it provides side-channel attack resistance, maintains functional correctness, and works seamlessly with the logic locking mechanism, thereby reducing the need for separate protection systems and minimizing hardware overhead
Data Source
AI summary
A method of state permutation logic locking (SPeLL) for sequential circuits. The method includes encrypting original states of a sequential circuit to produce encrypted states, by transitioning an initial order of the original states into a secret permutation of the encrypted states, where the secret permutation is different than the initial order. The method also includes determining a cryptographic key that corresponds to the transition from the initial order of the original states to the secret permutation of the encrypted states, and decrypting the encrypted states, by using the cryptographic key to transition from the secret permutation of the encrypted states back to the initial order of the original states.