Secure Test with RSNs: Seamless Authenticated Extended Confidentiality

Abstract

The testability of electronic devices is of critical importance and it is often supported by IEEE standards. The presence of test structures, on the other hand, paves the way for malicious attackers to access the circuit and extract confidential knowledge such as secret keys or intellectual property. Removing the access to these structures after manufacturing test may prevent security breaches, but this solution is not definitive and excludes the possibility of advanced uses such as online debugging, diagnosis of designs and on-line updates or monitoring. For this reason, it is important to maintain the test infrastructure but to protect it against threats either external (e.g., attackers) or internal (e.g., hardware trojans). This can be achieved through protocols ensuring authentication added to confidentiality capabilities. In the case of Reconfigurable Scan Networks (RSN -IEEE 1687), some solutions currently exist, but are limited to external threats. In this paper, we review the recent state of the art in the domain, and present a novel solution addressing in a comprehensive and low-cost manner authentication and confidentiality, both inside and outside the device.

Security EDA Extension through P1687.1 and 1687 Callbacks

“…In order to allow testing both secure and insecure IPs on the same scan path, cryptographic primitives should be placed at the interface of each protected segment: by doing so, insecure IPs would not be able to read the protected parts of the test vector. A first solution has been proposed in [13], where an Encryption SIB (eSIB) extends the Secure SIB (SSIB) [7], [8] to include encryption capabilities at negligible cost, but with an additional dynamic constraint. The cost is very low due to the reuse of authentication circuitry.…”

“…Encryption SIB: custom callbacks The Encryption SIB (eSIB), introduced in [13], is probably the first attempt to combine Authentication and IP-level Encryption. It only requires two more gates with respect to a S 2 IB, as illustrated in Figure 13.…”

“…This is not true anymore when the streamer acts in the middle of the chain: the symmetry is broken, and each bit will be treated differently depending on its position relative to the streaming module. Figure 15 provides a graphical representation of the analytical equations given in [13]. In relation to Figure 15-a), the "Protected" bits are treated as usual: data coming "fromSUT" and going "toSUT" is encrypted/decrypted when passing through the XOR gates at the input/output if the Streamer '(in this case, the eSIB).…”

“…As for the Streamer, it just needs four Callbacks: -CurrentMask(), NewMask(MaskBits) and ApplyMask(PlainText, Mask), which can be used by the Tool to implement the masking following the equation of [13] and Figure 12 -ResetProtocol(InitializationVector), that the Tool can use to synchronize its own Cypher with the one inside the SUT. The last step is the position of the Encrypted SIB inside the scan chain.…”