Better Not to Know?: The SHA1 Collision & the Limits of Polemic Computation

In February of 2017, Google announced the first SHA1 col- lision. Using over nine quintillion computations (over 6,500 years of compute time), a group of academic and industry researchers produced two different PDF files with identical SHA1 checksums. But why? After all, SHA1 had already been deprecated by numerous standards and advisory bodies. This paper uses the SHA1 collision compute as a site for surfacing the space of ecological risks, and sociotechnical rewards, associated with the performance of large computes. I forward a theory of polemic computation, in which com- putes exert agency in sociotechnical discourses not through computational results, but through feats, the expenditure of significant material resources. This paper does not make specific claims about the (ecological, political, labor) limits within which polemic computes must operate in order to be considered acceptable. Instead, this paper raises the question of how such limits could be established, in the face of polemic computes' significant costs and difficult-to-measure rewards.