Encryption

When information is passed from one party to another, and a 
third party is used during the transfer, then the information 
leaves the control of the sender. 
It can be :
·	read, 
·	altered, 
·	lost 
·	or delayed.  

If the information is important and private then the contents 
have to be secured (hidden).

The contents are coded or encrypted.
       
    Eg.   A becomes B,   B becomes C,   C becomes D,  etc….

             Therefore  CAB  becomes DBC.

To decode or de-encrypt you simply reverse the process.

Information that needs to be secured includes:

·	Trade secrets 	eg. (the Coca-Cola formulae)
·	Financial data 	       (ATM transactions)
·	Private details 	       (your payslip information)
·	National defense	       (the location of all the missiles)

People (spys, hackers, opportunists, and those who have 
accidents) are able to read and alter data on computer 
systems unless the data is protected.  We can use 
passwords and encryption to hide data.  Passwords alone 
are not enough, because some-one with access to the password
 file can control the system.  But if the passwords and
 the data is encrypted then having access to the 
password file get you knowhere.



When information is handled by a computer system, and the 
information needs to be restricted in any way, then a form of
 security needs to be implemented.  

Third party access in computer systems happens in areas where
 the data is available to outsiders. 

This occurs:
·	When files are passed across a network.(LAN or web)
·	When unknown people have access to the network terminals.
·	When Emails are sent.
·	When chatting/or conferencing  occurs.
·	When files are backed-up.  
·	When  Computer and Network administration is inadequate.

There is no perfect encryption method.  Given enough computer
 power and enough time, every code can be cracked. 
 However there is a point where the effort outweighs the
 benefit.  Therefore by having encryption at a very high level
 there is a deterrent to most hackers.   
The other
 factor is people.  Can they keep the codes secret. 

The old saying is;   "Its not that I can't keep a secret; It's the 
people I tell it to that can't keep the secret".

How does encryption work.










How does encryption work.

The basic encryption is done by character displacement.  There 
is a process and some rules.  The first  letter is replaced by 
the next letter in the alphabet.  The next letter is replaced by
 the previous letter in the alphabet, etc ……

(next letter) F

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
          ¯
B C D E F G H I J K L M N O P Q R S T U V W X Y Z A


(Previous letter) R

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
          						¯
Z A B C D E F G H I J K L M N O P Q R S T U V W X Y 


(next letter) E

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
        ¯
B C D E F G H I J K L M N O P Q R S T U V W X Y Z A


(Previous letter) D

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
      ¯    						¯
Z A B C D E F G H I J K L M N O P Q R S T U V W X Y 








FRED  becomes  GQFC

Send the message (GQFC)  -----à

To de-encrypt    
Reverse the process

GQFC  becomes FRED.

The process and rules are known as an algorithm.

For a computer this Algorithm could be cracked in a flash.  

Using the same algorithm it can be further complicated by 
introducing a password (code).   Lets say that rather using 
the previous or next letter that you used the numbers in the
 password and counted back or forward as many letters
 as there numbers dictated.

Lets say the password is 46

Now the process and rules are.  The first  letter is replaced by 
the 4th letter ahead in the alphabet.  The next letter is 
replaced by the 6th letter back in the alphabet, etc ……

(4th letter ahead) F

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
          ¯
E F G H I J K L M N O P Q R S T U V W X Y Z A B C D


(6th letter back) R

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
          						¯
U V W X Y Z A B C D E F G H I J K L M N O P Q R S T 

(4th letter ahead) E

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
        ¯
E F G H I J K L M N O P Q R S T U V W X Y Z A B C D


(6th letter back) D

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
      ¯    						
U V W X Y Z A B C D E F G H I J K L M N O P Q R S T 


So FRED becomes JLIX

And you can now change the password(code) as often as you
 like to give a different encrypted message.

The person receiving the message needed to have the same
 password code, and they can de-encrypt the message.  

They may have a book of codes and depending on the date they
 choose a particular code.  Or the last message of the 
day tells them the code for tomorrow.

As long as it took longer than a day to crack the code then this 
method worked well.  The INIGMA codes used by Germany in
 the Second World War used a five number code, and they
 changed the password code book whenever they felt the
 messages were being cracked.  There were only a few
 days  when the code-breakers got lucky, otherwise the system worked well.
 That is until a computer was developed(invented) to
 help crack the message.  This machine was arguably
 the first electronic computer.