[W/K] :: RSA encryption

  RSA encryption
       
           A public-key cryptosystem for both
          encryption and authentication, invented in 1977 by Ron
          Rivest, Adi Shamir, and Leonard Adleman.  Its name comes from
          their initials.
       
          The RSA algorithm works as follows: take two large prime
          numbers, 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 one could factor n into p and q, however, then one
          could obtain the private key d.  Thus the entire security of
          RSA depends on the difficulty of factoring; an easy method for
          factoring products of large prime numbers would break RSA.
       
          http://www.rsa.com/rsalabs/faq/faq_home.html).html">RSA FAQ (http://www.rsa.com/rsalabs/faq/faq_home.html).
       
          (2002-03-29)