Waters said the system would be secure against so-called colluding users. If two people with different credentials tried to use them in combination to access encrypted data not available for people in their position, they would not get access, he said.

Waters' vision is that this principle of functional encryption could one day work with any function. A possible application would be in image encryption, Waters said. With this it would, for example, be possible to partially decrypt a picture of a group of people. Only a user who has been identified by facial recognition software could then see exactly the part of the image that shows him. "At the moment we cannot do this, but I believe we will be able to someday," Waters said.

Waters said he was proud of the fellowship. "The interview process was very challenging and getting the grant for unrestricted use means they trust you and believe in your work," he said.

Waters said he has not decided yet how he'll spend the US$200,000 grant coming with the Microsoft fellowship. He said maybe he would use a part of it to fund a sabbatical leave. "I enjoy doing research at the University of Texas at Austin and I like teaching -- but it would be great to clear my schedule for maybe a year to have time to think and work closely with some researchers in California I have a special relationship with," he said.

Waters received his Ph.D. and Master of Arts in computer science from Princeton University in 2004 and 2002, respectively. In 2000 he finished his Bachelor of Science in computer science at the University of California, Los Angeles.