Signing the certificate
=======================
                                              
     Certificate                              
   +------------------------------------+     
   | +--------------------------------+ |     
   | |     Subject Identification     | |     
   | |          Information           | |     
   | +--------------------------------+ | 
   | +--------------------------------+ |      +-----------------+
   | |        Subject Public          | |      |                 |
   | |          Key Value             |-|----->|  Message Digest |
   | +--------------------------------+ |      |    Algorithm    |
   | +--------------------------------+ |      |   (e.g. SHA1)   |
   | |   Certfication Authoritiy's    | |      +-----------------+
   | |             Name               | |               |
   | +--------------------------------+ |               |
   |               ....                 |               |
   | +--------------------------------+ |               v         +--------------+
   | |   Certification Authority's    | |           o-------o    /Certification /  
   | |        Digital Signature       |<|-----------|encrypt|<--/  Authority's /  
   | +--------------------------------+ |           o-------o  /   Private Key/    
   +------------------------------------+                     +--------------+    


Verifying the certificate
=========================

                                              
     Certificate                              
   +------------------------------------+     
   | +--------------------------------+ |     
   | |     Subject Identification     | |     
   | |          Information           | |     
   | +--------------------------------+ |      +-----------------+
   | +--------------------------------+ |      |                 |
   | |        Subject Public          | |      |  Message Digest |
   | |          Key Value             |-|----->|    Algorithm    |
   | +--------------------------------+ |      |   (e.g. SHA1)   |
   | +--------------------------------+ |      +-----------------+
   | |   Certfication Authoritiy's    | |               ||        
   | |             Name               | |               vv
   | +--------------------------------+ |               <>  equal == valid
   |               ....                 |               ^^ 
   | +--------------------------------+ |               ||        +--------------+
   | |   Certification Authority's    | |           o-------o    /Certification / 
   | |        Digital Signature       |-|---------->|decrypt|<--/  Authority's /  
   | +--------------------------------+ |           o-------o  /   Public Key /   
   +------------------------------------+                     +--------------+