SSSL: Secure Search Space Locking of Behavioral IPs

Raising the level of VLSI design abstraction from the register transfer level (RTL) to the behavioral level has multiple advantages: 1) It reduces the turn-around-time; 2) allows faster verification; and 3) extends the reusability of the design as high-level synthesis (HLS) automatically reoptimizes the synthesized circuit when new process technologies are available by simply selecting a different technology library. Moreover, HLS makes extensive use of synthesis directives that control how to synthesize mainly loops (unroll or pipeline), arrays (register or RAM), and functions (inline or not). This further increases the reusability of the behavioral code as it enables the generation of micro-architectures with different area versus performance tradeoffs. These advantages open the door to third-party IP (3PIP) vendors providing behavioral IPs (BIPs). Unfortunately, the market of third-party BIPs is still very small and mostly limited to the HLS vendors themselves. Being so flexible is also their main weakness as it makes them only economically viable if the BIP provider can charge a large premium as it is highly unlikely that the BIP consumer will require their service again. Traditional IP vendors discriminate the price of the IP based on the amount of flexibility of the IP, e.g., RTL description versus providing a synthesized gate netlist. We envision a similar price discrimination strategy for BIPs by limiting the reusability of the BIP by partially encrypting the BIP source code. The main idea is to limit the search space, and hence, the reusability of the BIP such that it only allows the BIP consumer to generate micro-architectures within a predefined search space range. This is accomplished by selectively fixing some of the synthesis directives in the form of pragmas at the source code while leaving others explorable. By encrypting the portion of the BIP that contains the fix pragmas we can guarantee that no designs outside of the predefined search space are generated. We believe that this work could serve as catalyst to grow the BIP market.