The country's Unified Payment Interface (UPI) debuted on Monday. It's a system designed to make transferring and receiving money as easy as exchanging e-mail or text messages. This may yank the country's cash-based economy into the 21st century and enable 1.2 billion people, many of whom have never seen a bank or opened an account, to send digital payments to each other. The UPI network is created by retail banks and backed by the RBI and they are confident that it would work because it's built on top of a comprehensive digital project: biometrics-enabled national ID system, called Aadhaar after the Hindi word for foundation. So far, the country's attempt to assign every citizen a unique 12-digit number associated with a person's unique iris, fingerprint or facial features, is succeeding. Last week, Aadhaar reached its milestone of registering 1 billion people. With more than 80 percent of Indians enrolled, it gives the payments system a solid base to build on. "The interface will bring banking to the unbanked," said Vinod Khosla, billionaire investor and co-founder of Sun Microsystems. His Bangalore-based incubator Khosla Labs is backing an Indian startup called Novopay, which offers mobile banking at 44,000 kiranas, or neighborhood convenience stores, in the country.