Computer science
- Created by: SouthoS01
- Created on: 17-10-19 11:00
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- Yr9 computer science
- Ciphers
- Substitution
- A substitution cipher is where you systematically substitute one character for another, often using a key
- Julius Caesar invented a type of substitution cipher called the Caesar cipher. This is where you shift each letter in the alphabet 3 times to the right against the same alphabet.
- Why?
- So the Roman army could communicate and send messages in this code without other spies understanding where or what the army would do next
- Why?
- A key is how many spaces you move the alphabet across
- Transposition
- A transposition cipher is a way of changing plain text into cipher text systematically by changing the position of letters in a word
- An example would be what the Greeks used using the Scytale roll
- Cipher text is the coded message
- Plain text is the normal, everyday text and characters that we use
- Cryptanalysis is the process to decipher a code without knowing the key
- Substitution
- Python
- Print: this then shows the text as part of the code when run
- " " " these allow the user to make notes or keep code but not allow it to run
- Variables: a storage area in the memory of a computer given a label. The contents of a variable can be changed throughout the program
- Data Types
- Real/float numbers are numbers with a decimal place
- Strings are lines that is a sequence of characters
- Integers are whole numbers that are above 0 and have no decimal places
- Loops
- while
- for
- Boolean is a variable that has two outcomes e.g. true or false
- if, elif, else
- if: runs when a statement becomes true
- elif: this runs when there is more than one option to happen, shortened version of else if
- else
- input()
- Ciphers
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