Public Key Cryptography In Summary

• A public key is used to encrypt and a separate, different private key to decrypt the message.
   
  
• Each party involved generates a key pair.
   
  
• Each party publishes their public key. This is made widely known to all potential communication partners.
   
  
• Each party secures their private key, which must remain secret.
   
  
• Assuming A desires to send a message to B, A first encrypts the message using B's public key.
   
  
• B can decrypt the message using its private key. Since no one else knows B's private key, this is absolutely secure -- no one else can decrypt it.
   
  
• There still remain difficult problems of authentication of public keys, compromised keys, bogus & out of date keys. Further, Public Key encryption is very, very slow compared to single key systems.
   
  
• A very useful and common way of using public key cryptography is as a means of establishing/distributing secret keys for conventional single key cryptography, see later.