The digital currency that utilizes blockchain for transactions is Bitcoin. As the first cryptocurrency, Bitcoin operates on a decentralized ledger technology that ensures transparent and secure peer-to-peer transactions without the need for intermediaries like banks. The blockchain records every transaction in a tamper-proof manner, enhancing trust and security while reducing fraud. Other cryptocurrencies, such as Ethereum and Ripple, also utilize blockchain, but Bitcoin remains the most recognized and widely used digital currency.