Mathematics set 2 Flashcards
What is encryption?
Encryption is making data safe and secret
What is decryption?
Decryption is the way to read the secret message.
When is encryption and decryption vitally important?
During wartime.
What was Bletchly Park?
Bletchly park was the center of encryption and decryption in England in World War 2
What is a cryptologist?
A cryptologist is a person who works to decrypt secret messages from the enemy or encrypts messages into code
What is the Enigma machine?
The Enigma machine was a cryptography machine created during WW2 by the Germans.
How did the Enigma machine work?
The Enigma machine used keyboard and a set of rotating disks and electric circuits created codes.
How did breaking the Enigma code help the war?
The British cryptographers broke the code and were able to find out the secret German messages, which helped them to win.
What is a substitution code?
A substitution code replaces a letter with another letter or symbol
How can a person decode a message written in a substitution code?
The person must need to know the replacement letters.
What is an encryption key?
An encryption key is the code of replacements for a particular code
What is a Caesar Shift Cipher?
A Caesar Shift Cipher replaces each letter with a letter a set distance away, and was used by Julius Caesar in Roman times.
How can a person try to break a code?
Look at the frequent symbols as the letter ‘e’ is most frequently used.
How can you make a code difficult to break?
Change as many letters as you can, so that it’s hard to find patterns.
what is the problem with a Frequency Analysis?
Looking for the most frequent symbols or letters can only work to break the code if the message is very long.
What is a symmetric key?
A Symmetric Key is used to make the message and to decode the message
What is a draw back of a Symmetric Key?
It is very simple
What is an uncoded message called?
An uncoded message is called plaintext
What is a public-key encryption?
Public-key encryption has two different keys, a public key to encrypt and a private key to decrypt
Why is public-key encryption safer?
Only the intended recipient getting the message knows the key to decrypt your message.
What is a compression code?
A compression code re-writes information using fewer characters, so it takes less space on a computer and can be transmitted more quickly
Wlcm to Chmns is what message?
Welcome to Chemainus with the vowels taken out.
What is a JPEG?
A JPEG is a digital photo image.
What does JPEG stand for?
Joint Photographic Experts Group, which is the name of the group that figured out how to compress images
What is Morse Code?
Morse code is a message system that uses electricity.
Who invented Morse Code?
Samuel Morse in 1844 invented Morse Code
What is the machine that sends Morse Code?
An electric telegraph machine sends Morse Code
How was Morse Code transmitted?
Morse code was transmitted over telegraph wires that carried electricity.
How does Morse Code work?
Each letter is replaced by a system of dots and dashes
Why is Morse Code a kind of compression code?
It is a compression code because the most used letters have the shortest sequences.
What is Run-length coding?
Run-length coding is used on a fax machine (facsimile machine)
How does a fax machine work?
A fax machine translates the image into sets squares in a fine grid, then sends the information as to whether the grid is full or not.
What is the Arecibo Message?
The Arecibo Message was a message sent into space using a radio telescope
How is regular coding different than run-length coding?
In regular coding you put a 0 if there is nothing in that spot, but a 1 if there is something in that spot, so it becomes a list of 0001110001110001010 etc. In run-length coding, you only put the number of the space that is full so 456 etc, so it takes less transmission space.
