Secured Test Pattern Generators for BIST

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.