Enlarge / Litecoin's price has doubled in the last 24 hours. (credit: CoinMarketCap) This month's cryptocurrency boom isn't limited to bitcoin. Over the last 24 hours, two of bitcoin's biggest rivals—Litecoin and Ethereum's ether—have enjoyed huge price gains. Trading volume has been so intense that one of the leading cryptocurrency exchange services, Coinbase, has suffered downtime. "Ethereum buys and sells are temporarily disabled," read a notice on the Coinbase status page around 2pm Eastern time.