Encryption

“the process of converting information or data into a code, especially to prevent unauthorized access.”

“the process of converting information or data into a code, especially to prevent unauthorized access.”

• Conversion is an important part of computer science.

• Any computer program is written in text and converted (properly known as compiled) into something else.

• Encryption involves conversion where an input value goes in and is processed into an output value.
• Encryption involves transforming a human readable piece of data into something that is unreadable.
• For example using an encryption method: 
   

• Alphabetic ciphers are so simple that they barely protect a message at all.
• All you do is replace each letter with a number.

• In around 50 BC, the Roman dictator Julius Caesar developed his own encryption method for communication with his front line commanders.
• This became known as the Caesar Cipher and was one of the earliest types of encryption.
• Although it is relatively simple, it was incredibly successful for Caesar.

• It works by shifting each character in the alphabet along. Caesar used a shift of three so A became D and B became E and F became I.
• By shifting the characters back the way the message could be decrypted and read.
• Spaces remain the same!
• If we shift each character in the alphabet along 4 we get:
   

• Book ciphers require a copy of a book that both parties have access to.

• To encrypt, you simply look for words you want in your message, then write the page number and the word number on the page.

• The book that is used to decrypt must be the exact same edition as the book used to encrypt as in most cases other editions will have slight alterations to them that could change the message.

• Decrypting these can be quite slow but it's a very secure algorithm.

• Spelling ciphers require a good understanding of spelling syntax in a language (such as English).

• You simply write the letter which has been added or omitted or switched around. 

• Whenever there is a switched spelling mistake you take the first letter of the switched word.

• During World War II encryption and decryption were very big parts of everyday battles to ensure that the enemy did not manage to get hold of vital information.

• The Germans invented a machine called an Enigma machine that was used to encipher and decipher messages.

• It is said that the war was shorted by several years thanks to Alan Turing's breaking of Enigma. 

• Have you ever noticed the little padlock at the top of the browser?

• Most of the world’s websites are now encrypted using public and private key encryption. We are not going to go into too much detail about this, however.
• In a nutshell, all that public key and private key encryption means is that all the data transmitted between the user’s web browser and the web server is encrypted.

• Browser cookies are small pieces of data that websites send and receive to and from the computer that has requested the website. They contain small amounts of data such as preferences or settings.

• Cookies can be used to track a computer system by adding a small piece of data that uniquely identifies the computer system (not the user). These cookies are known as tracking cookies.

• These tracking cookies can then figure out things about the user such as the pages they visit on the website (although there are other ways for them to do this, so disabling cookies does not prevent the user being tracked), their interests and the computer system being used.