Biblio

With the development in IC technology, testing the designs is becoming more and more complex. In the design, process testing consumes 60-80% of the time. The basic testing principle is providing the circuit under test (CUT) with input patterns, observing output responses, and comparing against the desired response called the golden response. As the density of the device are rising leads to difficulty in examining the sub-circuit of the chip. So, testing of design is becoming a time-consuming and costly process. Attaching additional logic to the circuit resolves the issue by testing itself. BIST is a relatively a design for testability technique to facilitate thorough testing of ICs and it comprises the test pattern generator, circuit under test, and output response analyzer. Quick diagnosis and very high fault coverage can be ensured by BIST. As complexity in the circuit is increasing, testing urges TPGs (Test Pattern Generators) to generate the test patterns for the CUT to sensitize the faults. TPGs are vulnerable to malicious activities such as scan-based side-channel attacks. Secret data saved on the chip can be extracted by an attacker by scanning out the test outcomes. These threats lead to the emergence of securing TPGs. This work demonstrates providing a secured test pattern generator for BIST circuits by locking the logic of TPG with a password or key generated by the key generation circuit. Only when the key is provided test patterns are generated. This provides versatile protection to TPG from malicious attacks such as scan-based side-channel attacks, Intellectual Property (IP) privacy, and IC overproduction.

The globalized supply chain in the semiconductor industry raises several security concerns such as IC overproduction, intellectual property piracy and design tampering. Logic locking has emerged as a Design-for-Trust countermeasure to address these issues. Original logic locking proposals provide a high degree of output corruption – i.e., errors on circuit outputs – unless it is unlocked with the correct key. This is a prerequisite for making a manufactured circuit unusable without the designer’s intervention. Since the introduction of SAT-based attacks – highly efficient attacks for retrieving the correct key from an oracle and the corresponding locked design – resulting design-based countermeasures have compromised output corruption for the benefit of better resilience against such attacks. Our proposed logic locking scheme, referred to as SKG-Lock, aims to thwart SAT-based attacks while maintaining significant output corruption. The proposed provable SAT-resilience scheme is based on the novel concept of decoy key-inputs. Compared with recent related works, SKG-Lock provides higher output corruption, while having high resistance to evaluated attacks.

Intellectual Property (IP) infringement including piracy and overproduction have emerged as significant threats in the semiconductor supply chain. Key-based obfuscation techniques (i.e., logic locking) are widely applied to secure legacy IP from such attacks. However, the fundamental question remains open whether an attacker is allowed an exponential amount of time to seek correct key or could it be useful to lock out the design in a non-destructive manner after several incorrect attempts. In this paper, we address this question with a robust design lockout technique. Specifically, we perform comparisons on obfuscation logic output that reflects the condition (correct or incorrect) of the applied key without changing the system behavior. The proposed approach, when combined with key obfuscation (logic locking) technique, increases the difficulty of reverse engineering key obfuscated RTL module. We provide security evaluation of DLockout against three common side-channel attacks followed by a quantitative assessment of the resilience. We conducted a set of experiments on four datapath intensive IPs and one crypto core for three different key lengths (32-, 64-, and 128-bit) under the typical design corner. On average, DLockout incurs negligible area, power, and delay overheads.