Adam Back: “21 takes us full circle from Hashcash to Bitcoin antispam” Posted on January 29, 2017 by 247 BTC 247 BTC Bitcoin News Search 1 News - 247 News - 247 Bitcoin - 1 Search Search for: submitted by /u/wegotothem00n [link] [comments] 247 BTC Bitcoin News Search 1 News - 247 News - 247 Bitcoin - 1 Search Search for: