(In maths jargon, this is called the modulus.) For instance, 6 divided by 4 equals 1 with a remainder of 2. Remember learning fractions and decimals? Divide a large number by a small number and you can end up with leftovers. The answer to this calculation is still pretty big (498,430,667,329.9412) - but in fact, all I'm interested in is the remainder. I then divide this massive number by your N (187). In other words, I multiply 99 x 99 x 99 x 99 x 99 x 99 x 99 (seven times) and end up with a very large number. I raise my message to e (it's an exponential, get it?). I look you up on a directory and find your public key - your N and e - 187,7. (Even if the message isn't a number, it can easily be represented as one your phone or computer has made that conversion for you to read this article.) Now I'm going to send you a message outlining how many bottles of beer are on the wall - 99, of course - but we don't want anyone else to know. Now publish N and e wherever you like - shout them from the rooftops if you want - but 'you'd usually publish it on an online directory just like a telephone number', Professor Batten said. There are some rules that restrict your choice*, but let's say you pick 7.Ĭongratulations! You've now set up your encryption scheme. Your second public number is a smaller one, which you can choose, and goes by the nickname e. Let's call this value N - it's one of your public key numbers. The RSA algorithm was named after the three mathematicians who first publicly unveiled it in 1977.Īnd how can the Government get their hands on everyone's messages? Read more Prime numbers are fundamental to the most common type of encryption used today: the RSA algorithm. So why is that? Introducing the RSA algorithm The rest, like 4 for instance, are not prime: 4 can be broken down to 2 times 2, as well as 4 times 1.īut when mathematicians and computer scientists talk about large prime numbers - hundreds or thousands of digits long - it's often in the context of encryption: big primes, they say, help send secure messages between people, or computers. The first few primes are 2, 3, 5, 7 and 11. If you need a refresher on the definition of a prime number, it's a number larger than 1 that's divisible only by itself and 1. On 26 December, mathematicians scored a late Christmas present when a computer owned by a 51-year-old engineer in the US discovered the numerical beast, which starts with a 4 and ends in 1 - with 23,249,423 digits in between. Don't know if you've heard, but there's a new largest known prime number in town.

Who uses rsa encryption