A system on chip includes a one-time programmable (OTP) memory configured to store secure data, an OTP controller including at least one shadow register configured to read the secure data from the OTP memory and to store the secure data, a power management unit configured to receive an operation mode signal from an external device and to output test mode information indicating whether an operation mode is a test mode according to the operation mode signal and a test valid signal corresponding to the secure data, and a test circuit configured to receive the test mode information from the power management unit, to receive test data from the external device, and to output a scan mode signal and a test mode signal according to the test data and a test deactivation signal, wherein the test deactivation signal corresponds to development state data indicating a chip development state in the secure data.

One aspect provides an FPGA chip mounted on a printed circuit board (PCB). The FPGA chip can include a joint test action group (JTAG) interface comprising a number of input/output pins and an enablement pin, and a control logic block coupled to the enablement pin of the JTAG interface. The control logic block can receive a control signal from an off-chip control unit and control a logical value of the enablement pin based on the received control signal, thereby facilitating the off-chip control unit to lock or unlock the JTAG interface. The FPGA chip can further include a detection logic block to detect an unauthorized access to the FPGA chip. An input to the detection logic is coupled to the enablement pin, and a conductive trace coupling the input of the detection logic block and the enablement pin is situated on an inner layer of the PCB.

A device includes a scan chain including a plurality of storage elements and an output buffer; a shadow shift register having a shadow shift input coupled to a scan output of one of the storage elements of the scan chain; a signature register; and a comparator having a first input, a second input, and an output. The comparator first input is to receive a value of the shadow shift register, and the comparator second input is to receive a value of the signature register. The output buffer has a control input coupled to the comparator output, and the output buffer provides a high-impedance output responsive to the value of the shadow shift register being unequal to the value of the signature register.

Certain aspects of the disclosure are directed to methods and apparatuses of intrusion detection for integrated circuits. An example apparatus can include a wired communications bus configured and arranged to carry data and a plurality of integrated circuits. The plurality of integrated circuits can include a first integrated circuit configured and arranged to operate in a scan mode during which the first integrated circuit performs a scan test to detect one or more faults in circuitry of the plurality of integrated circuits. The plurality of integrated circuits can further include a second integrated circuit configured and arranged to operate in a mission mode and supervise data traffic by monitoring communications including data patterns and accesses on the wired communications bus. In response to identifying a suspected illegitimate access, the second integrated circuit can perform a security action to mitigate a suspect illegitimate action in the plurality of integrated circuits.

A method includes configuring a first set of blocks of a plurality of blocks of an IC chip as secure data blocks, and configuring a second set of blocks of the plurality of blocks as non-secure data blocks. The method further includes receiving a test mode entry request in the IC chip. In response to the IC chip receiving the test mode entry request, carrying out a data-initialization operation on the plurality of blocks independently of whether any blocks of the plurality of blocks are configured as the secure data blocks or the non-secure data blocks. An IC chip data output is disabled during the data-initialization operation.

Various embodiments of the present disclosure provide a scan-based architecture for register-transfer-level (RTL) or gate-level designs that improves the security of scan chain-based design-for-testability (DFT) structures. In various embodiments, the scan-based architecture includes invisible scan chains that are hidden in such a way that an attacker cannot easily identify or locate the invisible scan chains for exploitation and revealing internal secure information of the design. The invisible scan chains are dynamically configurable into a scan chain with select flip-flops, such that scan paths of the invisible scan chains may be different between different designs, chips, or testing operations. Various embodiments further employ key-based obfuscation by combining a scan control finite state machine with existing state machines within a design, which improves design security against unauthorized use and increases confidentiality. Specific sequences of key patterns cause the design to transition into a test mode or a normal mode.

Various examples of a circuit and a technique for testing the circuit are disclosed herein. In an example, the circuit includes a data input coupled to a scan multiplexer and a path select multiplexer. The circuit further includes a scan-in input coupled to the scan multiplexer and to receive a value of a scan pattern. The circuit further includes a scan latch to store the value that has an input coupled to the scan multiplexer and an output coupled to the path select multiplexer. The scan multiplexer selects a first signal from the data input and the scan-in input and provides the first signal to the input of the scan latch. The path select multiplexer selects a second signal from the data input and the output of the scan latch and provides the second signal to a data output of the circuit.

A scan flip-flop configured to generate physically unclonable function (PUF) data according to the present disclosure includes a multiplexer configured to provide an internal signal through an input switch, a first latch circuit configured to latch the internal signal, wherein the first latch circuit comprises a first inverter, a second inverter, a first switch connected in parallel with the first inverter, and a second switch connected in series with the second inverter. Additionally, a second latch circuit configured to latch an output of the first latch circuit and output a latched value, wherein the second latch circuit comprises a third inverter, a fourth inverter, an output inverter connected in series with the third inverter, and a fourth switch connected in series with the fourth inverter. A third switch is configured to switch between the first latch circuit and the second latch circuit.

A Joint Test Action Group (JTAG) communication lockout processor is disclosed. The processor is configured to generate a unlock sequence based on an operational mode change of an operably connected programmable device, and save the unlock sequence to one or more memory registers. The processor can also receive an execution of the unlock sequence via a dual function JTAG communication bus, determine, via an unlock logic, whether the execution of the unlock sequence is valid, and responsive to determining that the execution of the unlock sequence is valid, allow or disallow the JTAG communication with an embedded processor.

Various aspects of the disclosed technology relate to techniques of using control test points to enhance hardware security. The design-for-security circuitry reuses control test points, a part of design-for-test circuitry. The design-for-security circuitry comprises: identity verification circuitry; scrambler circuitry coupled; and test point circuitry. The test point circuitry comprises scan cells and logic gates The identify verification circuitry outputs an identity verification result to the scrambler circuitry to enable/disable control test points of the test point circuitry through the logic gates, and the scrambler circuitry outputs logic bits for loading the scan cells to activate/inactivate the control test points through the logic gates.