Synthesis and verification of cyclic combinational circuits

Chen, Jui-Hung; Chen, Yung-Chih; Weng, Wan-Chen; Huang, Ching-Yi; Wang, Chun-Yao

doi:10.1109/socc.2015.7406959

Cited by 7 publications

(6 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A Boolean function does not need to be acyclic. Furthermore, it is possible to reduce the number of gates in a circuit if a function could be implemented in its acyclic form [37][38][39][40]. For example, the work in [40] presents an n-input 2n-output positive unate Boolean function which can be realized with 2n two-input gates when feedback is used but requires 3n − 2 gates if the feedback is not used.…”

Section: B Building Cyclic Boolean Functionsmentioning

confidence: 99%

“…3) Node-merging based cycle generation: The third approach for cyclification of a netlist is based on the work in [37] where the logic implication is used to identify cyclifiable structure candidates directly, or to create them aggressively in circuits. At its core, the work in [37] introduces active combinational feedback cycles by merging two nodes in the original DAG. To check the validity of the generated cyclic netlist, they use a SAT-based algorithm and validate whether the formed cycles are combinational or not.…”

Section: )mentioning

confidence: 99%

“…To prevent template scanning and removal attacks, in a subsequent camouflaging step (using the gate and route obfuscation) the template will be hidden. Note that many such templates could be made [37][38][39][40], and by not knowing the template type and the camouflaged technique used to hide the connection, an attacker can not identify and remove these templates.…”

Section: ) Template-based Cyclic-function Mappingmentioning

confidence: 99%

See 2 more Smart Citations

SAT-Hard Cyclic Logic Obfuscation for Protecting the IP in the Manufacturing Supply Chain

Roshanisefat

Kamali

Homayoun

et al. 2020

IEEE Trans. VLSI Syst.

View full text Add to dashboard Cite

State-of-the-art attacks against cyclic logic obfuscation use satisfiability solvers that are equipped with a set of cycle avoidance clauses. These cycle avoidance clauses are generated in a pre-processing step and define various key combinations that could open or close cycles without making the circuit oscillating or stateful. In this paper, we show that this preprocessing step has to generate cycle avoidance conditions on all cycles in a netlist, otherwise, a missing cycle could trap the solver in an infinite loop or make it exit with an incorrect key. Then, we propose several techniques by which the number of cycles is exponentially increased as a function of the number of inserted feedbacks. We further illustrate that when the number of feedbacks is increased, the pre-processing step of the attack faces an exponential increase in complexity and runtime, preventing the correct composition of cycle avoidance clauses in a reasonable time. On the other hand, if the pre-processing is not concluded, the attack formulated by the satisfiability solver will either get stuck or exit with an incorrect key. Hence, when the cyclic obfuscation under the conditions proposed in this paper is implemented, it would impose an exponentially difficult problem for the satisfiability solver based attacks.

show abstract

Section: B Building Cyclic Boolean Functionsmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

Section: ) Template-based Cyclic-function Mappingmentioning

confidence: 99%

See 1 more Smart Citation

SAT-Hard Cyclic Logic Obfuscation for Protecting the IP in the Manufacturing Supply Chain

Roshanisefat

Kamali

Homayoun

et al. 2020

IEEE Trans. VLSI Syst.

View full text Add to dashboard Cite

show abstract

“…A Boolean function does not need to be acyclic; it is possible to reduce the number of gates in a circuit if a function could be implemented in its acyclic form [2][1][9] [10]. For example, the work in [10] presents an n-input 2n-output positive unate Boolean function which can be realized with 2n two-input gates when feedback is used but requires 3n − 2 gates if feedback is not used.…”

Section: Building Cyclic Boolean Functionsmentioning

confidence: 99%

“…Node-merging based cycle generation. The third approach for cyclification of a netlist is based on the work in [2] where the logic implication is used to identify cyclifiable structure candidates directly, or to create them aggressively in circuits. At its core, the work in [2] introduces active combinational feedback cycles by merging two nodes in the original DAG.…”

Section: 23mentioning

confidence: 99%

SRCLock: SAT-Resistant Cyclic Logic Locking for Protecting the Hardware

Roshanisefat,

Kamali,

Sasan

2018

Preprint

View full text Add to dashboard Cite

In this paper, we claim that cyclic obfuscation, when properly implemented, poses exponential complexity on SAT or CycSAT attack. The CycSAT, in order to generate the necessary cycle avoidance clauses, uses a pre-processing step. We show that this pre-processing step has to compose its cycle avoidance condition on all cycles in a netlist, otherwise, a missing cycle could trap the SAT solver in an infinite loop or force it to return an incorrect key. Then, we propose several techniques by which the number of cycles is exponentially increased with respect to the number of inserted feedbacks. We further illustrate that when the number of feedbacks is increased, the pre-processing step of CycSAT faces an exponential increase in complexity and runtime, preventing the correct composition of loop avoidance clauses in a reasonable time before invoking the SAT solver. On the other hand, if the pre-processing is not completed properly, the SAT solver will get stuck or return incorrect key. Hence, when the cyclic obfuscation in accordance to the conditions proposed in this paper is implemented, it would impose an exponential complexity with respect to the number of inserted feedback, even when the CycSAT solution is used.

show abstract