  This paper systematizes knowledge about secure software supply chain
patterns. It identifies four stages of a software supply chain attack and
proposes three security properties crucial for a secured supply chain:
transparency, validity, and separation. The paper describes current security
approaches and maps them to the proposed security properties, including
research ideas and case studies of supply chains in practice. It discusses the
strengths and weaknesses of current approaches relative to known attacks and
details the various security frameworks put out to ensure the security of the
software supply chain. Finally, the paper highlights potential gaps in actor
and operation-centered supply chain security techniques
