RERTL: Finite State Transducer Logic Recovery at Register Transfer Level

Increasingly complex Intellectual Property (IP) design, coupled with shorter Time-To-Market (TTM), breeds flaws at various levels of the Integrated Circuit (IC) production. With access to IPs at all stages of production, design defects can easily be found and corrected, i.e., knowledge of the Register Transfer Level (RTL) code allows for the option of easy defect detection. However, third-party IPs are typically delivered as hard IPs or gate-level netlists, which complicates the defect detection process. The inaccessibility of source RTL code and the lack of RTL recovery tools make the task of finding high-level security flaws in logic intractable. Upon this request, in this paper, we present an RTL recovery tool suite named RERTL that leverages advanced graph algorithms including Lengauer-Tarjan's dominator tree and Euler tour tree technique to assist in netlist analysis. Supported by RERTL, logical states and their interactions are recovered from the initial design in the format of gate-level netlists. After the recovery of state interaction, RERTL further converts the full design into human-readable RTL. A series of netlist case studies were examined using RERTL covering benign logic structures, designs with accidental defects, and designs with deliberate backdoors. The experimental results show that all of our designs at various complexities were recoverable within seconds.