[Kikawala]

We publish this work as responsible disclosure. While a full SHA-256 collision (sr = 64) has not yet been achieved, the tools and techniques presented here represent significant methodological advances that bring it closer. Organizations relying on SHA-256 for collision resistance should begin evaluating migration paths to SHA-3 or other post-quantum hash functions. The cryptographic community should treat the collision resistance of SHA-256 as having a finite and shrinking safety margin.