Fixpoint

I intended to briefly introduce and present my implementation of the Keccak family of cryptographic hash functions today. A relatively small and self-contained piece of code, doing a well-defined thing, solving a well-understood problem... should be easy, right? Or so I thought, for about two minutes.

As I considered what context would be necessary even for readers already educated in "wtf are hash functions?", it soon blew up into a whole web of connected topics: some already written up elsewhere, some clear enough in my head to write up now, some needing a refresher, and some requiring further research.

There'd be history of Keccak itself; history of its interest to the forum, including why not SHA3; the seeming lack of a spec in place of SHA3 for "last hundred yards" questions like byte order and parameter selection; the degree to which the original paper does or doesn't help with those questions; history of interest in the Ada programming language in the forum; how I wanted to embrace it but was averse to accepting GNAT; approaches I made to that problem; an attempt I made to tidy up an older Keccak implementation; deciding to do my own in C; the level I aim to work at in that language regarding support libraries and why; my experience of reading the Keccak paper and filling in knowledge gaps; my observations in comparing it with SHA3; how I approached the parameter question and what remains open there; the process of implementing, mistakes made and tracking them down. Then could come presentation of the code itself, noting requirements, tested platforms and observed performance.

Perhaps I've now exaggerated the problem a wee tad; surely something sensible could be produced with a scope in between "everything that could possibly be said" and "here's some code: good luck". Certainly the debts of my past writing avoidance are making themselves felt. I hope I've at least better illuminated for myself a path out of the pit and provided a hint of things to come. Onwards!