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WWWE Logo RSA Encryption

RSA encryption is a public-key encryption and authentication system. RSA is used in a wide variety of products from such companies as Microsoft, Apple, Sun, and Novell. Both PGP and PEM use RSA encryption.

URLs:

RSA's Frequently Asked Questions About Today's Cryptography

W3E References:

PEM/PGM
PEM and PGM both utilize RSA encryption.

Detail:

RSA was invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman--hence its name. RSA encryption is a two-key system using both a private and a public key. Anyone can send an encrypted message or verify a signed message using public keys, but only someone in possession of the correct private key can decrypt or sign a message. Encryption and authentication take place without any sharing of private keys: each person uses only public keys and his or her own private key.

RSA works as follows: Take two large primes, p and q, and find their product n = pq; n is called the modulus. Choose a number, e, less than n and relatively prime to (p-1)(q-1), and find its inverse, d, mod (p-1)(q-1), which means that ed = 1 mod (p-1)(q-1); e and d are called the public and private exponents, respectively. The public key is the pair (n,e); the private key is d. The factors p and q must be kept secret, or destroyed.

It is difficult (presumably) to obtain the private key d from the public key (n,e). If you could factor n into p and q, however, you could obtain the private key d. So the entire security of RSA is predicated on the assumption that factoring is difficult; an easy factoring method would "break" RSA.

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Copyright 1996 Charles River Media. All rights reserved.
Text - Copyright © 1995, 1996 - James Michael Stewart & Ed Tittel.
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Revised -- February 20th, 1996