English National Curriculum:
Key Stage 2
Tooltip content
Use logical reasoning to predict the behaviour of simple programs
learning objectives
Tooltip content
To have a basic understanding of Caesar Cipher Rings and to understand why it is needed.
success criteria
- I can recognise a scenario where a code or secret message is used.
- I can understand a Caesar Cipher.
- I can perform encoding and decoding using a Caesar Cipher Ring.
top tips
- A repeating pattern is a part of a sequence that is repeated more than once.
- The number of repetitions is the time that a repeating pattern has been duplicated.
- Using a repeating pattern and number of repetitions will simplify and shorten the program.
Common misconceptions
- Caesar Cipher Messages are very difficult to understand.
- There are many convenient ways to decode messages using Caesar Ciphers and keys, it just requires time and accuracy.
Caesar Cipher
Key Shift or Shift
A Caesar cipher, or shift cipher is a primitive form of encryption named after Julius Caesar who used the algorithm to encrypt his letters
A loop is a sequence of instructions that is continually repeated until a certain condition is reached.
previous knowledge
Coded messages can be used to show how data can be represented in many different forms and languages. These forms can be changed and distilled into core elements that all programming languages use.
TOPIC BACKGROUND READING
A Caesar cipher, or shift cipher is a primitive form of encryption named after Julius Caesar who used the algorithm to encrypt his letters. The algorithm turns plaintext into ciphertext by shifting the letters of the plaintext forward along the alphabet.
The biggest benefit of the Caesar cipher is how easy it is to use. A short message can be encrypted and decrypted in your head, and even longer messages only need a paper and pencil.
The ciphertext is well enough obfuscated that it is unreadable to most people at a glance. This makes it useful for displaying text in public while preventing a passerby from casually understanding it. It is frequently used on forums and in hint books to hide content spoilers, and used on things like children’s decoder rings to teach them basic cryptography.
All that is needed to encrypt or decrypt a message is the message itself and the shared key or shift value.
