Rivest Shami Adleman (RSA) method

Public key encryption method used in pretty good privacy (PGP) and secure electronic commerce (SEC), and a part of ANSI, ISO and other international encryption standards. RSA is based on the simple arithmetical fact that it is relatively easy to multiply two large prime numbers but extremely difficult to work backward from the product to find those prime numbers. This technique allows the unique public encryption key (the product of prime numbers) to be disclosed to any one but which can be decoded only with the secret private key (the prime numbers). RSA key size falls between 768 and 2,048 bits; thus, there can be 22048 possible combinations a truly astronomical number that can resist practically any 'brute force' code-cracking attempt. Released in 1977, RSA is named after its inventors: Ron Rivest, Adi Shamir, and Leonard Adleman.