1.6 Encryption

History of Encryption

"As long as man has needed to send messages, he has needed to disguise them."

Cryptography is the science of information security and dates all the way back to Ancient Egypt.

The word comes from the Greek word Kryto meaning hidden.

Although the methods of encryption have become ever more sophisticated, the basic process remains the same today in high tech computer encryption as it did in ancient civilizations.

The original message is begins in what is referred to as PLAIN TEXT
A CIPHER is used to encode the message into CIPHER TEXT
The CIPHER TEXT is sent out into the wide world to be delivered to the intended recipient
- At this point it is easily intercepted by enemies
The intended recipient decodes the received CIPHER TEXT using the reverse CIPHER,
The resultant PLAIN TEXT can now be read

Hieroglyphics

The earliest known encryption was found in Ancient Egypt around 2000 BC,

in the form of complex pictograms called Hieroglyphics.

Although these could be seen by all, only an elite handful could interpret their full meaning.

In fact, these messages can still be seen to this day.

Scytale

Another simple method used in various parts of the world was Scytale.

Employed around 500 BC, by the Spartan military to encode messages between commanders

This involes a thin strip being wound around a stick with a set circumference.
Once wound round the stick, the message was written across the strip.
This was then sent (often as a belt) with a messenger
The recipient would wind the belt back around a stick of the same size and read the message.

Caesar Shift

ENIGMA Code and Colossus (the first electronic computer)

During WWII, the German military used complex Enigma machines to encode messages between military commanders.

The British built a 2KB computer to speed up cracking these codes.

- - - - The enigma machine consisted of 3 alphabet wheels
        Each letter in the wheel was randomly wired to a letter in the next wheel
        Additionally, after each letter was typed the wheel advanced one position
        This made it very difficult to crack the code and intercept Nazi messages.

NB The machine had approximately 1,000,000,000,000 combinations for the letters, making text frequency analysis impotent.

Public Private Key Encryption

Employed by the Romans circa 100 BC, this was used by Julius Caesar to communicate

with Governors of far flung provinces in the Roman Empire. Using two alphabet wheels to scramble and unscramble the messages.

The entire Latin alphabet was arranged in in a complete circle supplemented by a few numbers
A similar but smaller Alphabet circle, would fit inside it.
The position of the inner wheel was advanced by 3 letters in the alphabet.
Each letter of the message was advanced by 3 letters was then and sent
The recipient would then take each letter and decrease it by 3 positions to read the message

Cardan Grille

This system uses a mask applied to a page of writing to reveal the hidden message.It was invented around 1550 AD by Jerome Cardan.

- - - - A Cardan grille is made from a sheet of rigid paper,within which, rectangular areas are cut out at arbitrary intervals.
        An encipherer places the grille on a sheet of paper and writes his message in the rectangular apertures, some of which might allow a single letter, a syllable, or a whole word.
        Then, removing the grille, the fragments are filled out to create a note or letter that disguises the true message.

NB The recipient of the message must possess an identical grille.

This system commonly used today by governments, military, banking, business and even terrorists, uses pairs of matching keys.

The Public key is used to encode the message (this key is given out to all who wish to communicate with the user)
The encoded message is sent across the internet
The recipient uses the matching Private Key to decode the message.

NB The encryption key cannot be used to decode the message.

The matching key must be used.

Strong and Weak Encryption

Explanation of strong and weak

Encrytion and the Law

UK and US differing laws

1.6 (c)

Implications of Computer Use

c. discuss the effects on privacy and confidentiality of data held in computer systems, and steps which can be taken to protect confidentiality;.

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