Fast-food chain Burger King has launched its own crypto-currency, called WhopperCoin, in Russia.Customers will be able to claim one coin for every rouble (0.75p) they spend on the Whopper sandwich.Russians will be able to buy a Whopper with the virtual cash, once they have amassed 1,700 whoppercoins.The company said it would release Apple and Android apps next month so people could save, share and trade their wallet full of whoppercoins.Use and abuseBurger King has partnered with crypto-cash start-up Waves to create and run the scheme.The tech company will run the blockchain ledger for the coin to keep track of who has coins and what has been done with them. Customers will be able to claim their coins by scanning a receipt with a smartphone. The crypto-currency is a stand-alone system that has some technical similarities to Bitcoin but is distinct from it. This means the company would be able to shut the system down if it found it was being abused.In a statement, Waves said that it had already generated 1bn whoppercoins to use in the loyalty scheme. The current cost of a Whopper in Russia suggests customers will be able to get a free sandwich for every five or six they buy with real money.Ivan Shestov, head of external communications at Burger King Russia, said the scheme turned the Whopper into an “investment vehicle”.On social media, some people reported that they had already managed to claim whoppercoins after eating at a Burger King in Russia. Commenting on Twitter, Prof Emin Gun Sirer, from Cornell University and a director at the Initiative for Cryptocurrencies and Contracts, said there were likely to be launches of other schemes. “Reward points are actually a good use case for blockchains,” he said.However, in a later conversation, he warned that they could be used for money laundering and ransomware payments. “This will undoubtedly happen,” he said.