Digitally-Assisted Mixed-Signal Circuit Security

The design and manufacturing steps of a chip typically involve several parties. For example, a chip may comprise several third-party Intellectual Property (IP) cores and the Integrated Circuit (IC) fabrication may be outsourced to a third-party foundry. IP cores and ICs are shared with potentially untrusted third parties and, as a result, are subject to piracy attacks. Even more, any legally purchased chip may be reverse-engineered to retrieve the design down to transistor-level and, thereby, it is also subject to piracy attacks. In this paper, we propose MixLock, an anti-piracy countermeasure for mixed-signal IP cores and ICs. MixLock protection is based on inserting a lock mechanism into the design such that correct functionality is established only after applying a key which is the designer’s secret. The lock mechanism acts on the mixed-signal performances by leveraging logic locking of the digital part. MixLock presents several key attributes. It is generally applicable, it is non-intrusive to the sensitive analog section, it incurs no performance penalty and has very low area and power overheads, it is fully automated, and it is capable of co-optimizing security in both the analog and digital domains. We demonstrate MixLock on a Σ Analog-to-Digital Converter (ADC) using hardware measurements and an audio demonstrator.