This article has been so useful to me over the past 5 years. I've worked at a number of places that have tried building their own signing schemes and this, plus

This article has been so useful to me over the past 5 years. I've worked at a number of places that have tried building their own signing schemes and this, plus the definition of the later AWS Signatures that resulted, have helped build stronger solutions. Better yet, it's helped the company understand the risk with building anything crypto related yourself.