R.S.A. stands for Rivest, Shamir and Adleman - the three cryptographers who invented the first practical commercial public key cryptosystem. Today it is used in web browsers, email programs, mobile phones, virtual private networks, secure shells, and many other places. Exactly how much security it provides is debatable, but with sufficiently large keys you can be confident of foiling the vast majority of attackers. Until recently the use of RSA was very much restricted by patent and export laws. However, the patent has now expired and US export laws have been relaxed.

The basics of cryptography - Alice wants to talk to Bob, in private. more...
RSA Algorithm
A description of the algorithm, and a simple example of its use. more...
A simple implementation in Java, to demonstrate how this is done. more...
There are many practical issues to address when using cryptography, beyond just the algorithms. more...
A mathematical proof that RSA works, which I've made as simple as possible. more...

Further Reading

Two books I found very informative on this subject are:
  • Introduction to Algorithms, Cormen, Leiserson & Rivest
  • Applied Cryptography, Bruce Schnier
© 1998 - 2012 Paul Johnston, distributed under the BSD License   Updated:09 Apr 2009