Techniques and validation for protection of embedded processors

Abstract

Advances in technology scaling and miniaturization of on-chip structures have caused an increasing complexity of modern devices. Due to immense time-to-market pressures, the reusability of intellectual property (IP) sub-systems has become a necessity. With the resulting high risks involved with such a methodology, securing IP has become a major concern. Despite a number of proposed IP protection (IPP) techniques being available, securing an IP in the register transfer level (RTL) is not a trivial task, with many of the techniques presenting a number of shortfalls or design limitations. The most prominent and the least invasive solution is the integration of a digital watermark into an existing IP. In this thesis new techniques are proposed to address the implementation difficulties in constrained embedded IP processor cores.

This thesis establishes the parameters of sequences used for digital watermarking and the tradeoffs between the hardware implementation cost, detection performance and robustness against IP tampering. A new parametric approach is proposed which can be implemented with any watermarking sequence. MATLAB simulations and experimental results of two fabricated silicon ASICs with a watermark circuit embedded in an ARMR Cortex R-M0 IP core and an ARMR Cortex R-A5 IP core demonstrate the tradeoffs between various sequences based on the final design application. The thesis further focuses on minimization of hardware costs of a watermark circuit implementation. A new clock-modulation based technique is proposed and reuses the existing circuit of an IP core to generate a watermark signature. Power estimation and experimental results demonstrate a significant area and power overhead reduction, when compared with the existing techniques. To further minimize the costs of a watermark implementation, a new technique is proposed which allows a non-deterministic and sporadic generation of a watermark signature. The watermark was embedded in an ARMR Cortex R-A5 IP core and was fabricated in silicon. Experimental silicon results have validated the proposed technique and have demonstrated the negligible hardware implementation costs of an embedded watermark.

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