https://www.cnbc.com/2017/12/19/a-new-form-of-bitcoin-mining-patent-trolls-coming-for-the-blockchain.html >The blockchain, the digital ledger system that underlies the boom in cryptocurrencies like bitcoin, is an innovation born within the open-source software community, where software coders pride themselves on the sharing of information. But the blockchain's open-source formative years may not stay that way. >As bitcoin nears $20,000 and other digital currencies experience unprecedented gains, some of the biggest names in the corporate world are seeking patents related to the blockchain — financial companies like Visa, retailers like Walmart and the tech old guard like IBM. And in what likely would cause distress in the open-source movement, in late November one of the business world's most notorious patent trolls hatched plans to create and amass a trove of blockchain patents.