For more than 2000 years since the time of Greek mathematician Erathosthenes researchers have been examining prime numbers. These are the numbers which are divisible only by itself and 1. But until now it has been difficult to accurately determine which numbers are prime and which are not as the existing algorithims have a small chance of giving the wrong number or no number at all.

But now a computer science team from the Indian Institute of Technology in Kanpur led by Professor Manindra Agrawal have devised a computer programme which can quickly establish, with 100% accuracy, whether a number is a prime or not. The discovery is particularly useful for crytographers - code makers - who use prime numbers as the basis of many codes including encryption over the internet.

Source: New York Times