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1.3 ((encryption (asymmetric (it's impossible to work out the other…

- - - - symmetric encryption is one way, it requires the senders key to be sent with the encryption so they can decrypt it
        
        it can use the same key for each message or can have a unique key with each message
        
        key can be intercepted or copied to open decrypt the message
    - - it's impossible to work out the other key from one
      - key pairs public key any one can get it, private key secret
      - copy exchange of public keys
      - sender sends public key and recipient uses private key to decrypt it
      - no one will be able to read the message
      - message is authentic
      - sure message hasn't been modified
  - - - reduce download times
      - reduce requirements on file storage
      - make best use of band width
    - - actual data is removed from the file in order to reduce it's size
        
        algorithm is used to strip out the least important data
        
        typically used for multimedia files
        
        JPEG, MP3, MPEG
        
        original file cannot be restored
    - - actual data is still removed, however this data is encoded in such a way that the file size reduces and more importantly the original file size can be recreated exactly
        
        typically less effect at reducing size than lossy
        
        essential for some file types such as computer programs