Encryption

This lesson covers encryption — the process of converting plaintext into ciphertext to protect data from unauthorised access. You need to understand the Caesar cipher, Vernam cipher (one-time pad), symmetric and asymmetric encryption, and their use cases for the OCR H446 specification.

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What is Encryption?

Encryption is the process of transforming readable data (plaintext) into unreadable data (ciphertext) using an algorithm and a key. Only someone with the correct key can reverse the process (decryption) to recover the plaintext.

Key Terms

Term	Definition
Plaintext	The original, readable message
Ciphertext	The encrypted, unreadable message
Key	A value used by the encryption algorithm to transform the data
Encryption	The process of converting plaintext to ciphertext
Decryption	The process of converting ciphertext back to plaintext
Cipher	The algorithm used to perform encryption/decryption

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Caesar Cipher

The Caesar cipher is a simple substitution cipher that shifts each letter in the plaintext by a fixed number of positions in the alphabet.

How It Works