Today's blockchain and cryptocurrency news Bitcoin is down 1.5% at $8,610 XRP is down 2.5% 26 cents and Ethereum is down 1% at $186 Top gainers in the last 24 hours: Cortex up 48% and Dentacoin, up 15% Coinbase’s visa debit card has added support for XRP, BAT, Augur, Stellar and 0x. Iran has announced new power tariffs for crypto miners, and is offering a bounty for exposing illegal mining operations. Hackers are demanding 5 million in bitcoin as they hold Mexico’s national oil company Pemex in a cyberattack. Justin Sun has confirmed his involvement in the investor group that acquired Poloniex from Circle. Google is partnering with Citi bank to offer checking accounts under the moniker Cache.