Introduction to Cryptography
Cryptography uses mathematical principles including modular arithmetic, prime numbers, and number theory to encrypt and secure digital communications.
What You Need to Know
Key Concept Diagram
Modular arithmetic (clock arithmetic) finds the remainder after division: 17 mod 5 = 2
Prime numbers are the building blocks of cryptographic systems like RSA
A Caesar cipher shifts each letter by a fixed number of positions in the alphabet
Public key cryptography uses two keys: a public key to encrypt and a private key to decrypt
RSA encryption relies on the difficulty of factorising large numbers
Key Vocabulary
Modular arithmetic
Arithmetic where numbers wrap around after reaching a certain value (the modulus)
Cipher
A method of encrypting or decrypting messages
Encryption
The process of converting readable data into a coded form
Prime factorisation
Expressing a number as a product of prime numbers
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What is 23 mod 7?
Question 2
In a Caesar cipher with a shift of 3, the letter A becomes:
Question 3
Why are prime numbers important in RSA encryption?
Key Concepts Summary
- ●Modular arithmetic (clock arithmetic) finds the remainder after division: 17 mod 5 = 2
- ●Prime numbers are the building blocks of cryptographic systems like RSA
- ●A Caesar cipher shifts each letter by a fixed number of positions in the alphabet
- ●Public key cryptography uses two keys: a public key to encrypt and a private key to decrypt
- ●RSA encryption relies on the difficulty of factorising large numbers