DRAFT May 2019 A randomness beacon produces timed output so fresh public randomness. Each output, called a pulse, also includes metadata and cryptographic elements to support several security and usability features. This document specifies a reference "version2" of a format for pulses and of a protocol for beacon operations. The main goal of the description is to serve as a baseline for the deployment of numerous interoperable beacons, including the NIST Beacon. In the proposed reference, a Beacon periodically outputs a pulse containing 512 fresh random bits, time-stamped, signed and hash-chained. For example, each pulse also pre-commits to the randomness to be released in the next pulse. The latter enables users to securely combine randomness from different beacons. The Beacon protocol also specifies the interface for users to interact with the Beacon, in order to obtain information about past pulses. Why buy a book you can download for free? We print the paperback book so you don't have to. First you gotta find a good clean (legible) copy and make sure it's the latest version (not always easy). Some documents found on the web are missing some pages or the image quality is so poor, they are difficult to read. If you find a good copy, you could print it using a network printer you share with 100 other people (typically its either out of paper or toner). If it's just a 10-page document, no problem, but if it's 250-pages, you will need to punch 3 holes in all those pages and put it in a 3-ring binder. Takes at least an hour. It's much more cost-effective to just order the bound paperback from Amazon.com This book includes original commentary which is copyright material. Note that government documents are in the public domain. We print these paperbacks as a service so you don't have to. The books are compact, tightly-bound paperback, full-size (8 1/2 by 11 inches), with large text and glossy covers. 4th Watch Publishing Co. is a HUBZONE SDVOSB. https: //usgovpub.com Buy the paperback from Amazon and get Kindle eBook FREE using MATCHBOOK. go to https: //usgovpub.com to learn how