# Roger Wattenhofer - The Science of the Blockchain (Highlights) ![rw-book-cover|256](https://m.media-amazon.com/images/I/71g5HWj-nvL._SY160.jpg) ## Highlights - validity requirement ([Location 12235](https://readwise.io/to_kindle?action=open&asin=B01B5WMUT0&location=12235)) must be selected from inputs