Data Transmission · 4 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 4% of your exam marks.
Symmetric vs asymmetric encryption questions are growing as cybersecurity becomes more prominent.
Modern encryption splits into two big families, distinguished by how many keys are used.
| Symmetric encryption | Asymmetric encryption | |
|---|---|---|
| Number of keys | One | Two (a public key + a private key) |
| Key used to encrypt | The shared secret key | The recipient's public key |
| Key used to decrypt | The same shared key | The recipient's private key |
| Key shared with everyone? | No, must be kept secret | The public key can be shared freely; the private key must stay secret |
| Speed | Fast | Slower (more complex maths) |
| Main challenge | Sharing the key securely with the recipient | None: the public key can be sent openly |
| Examples | AES, DES, Wi-Fi (WPA2) | RSA, ECC, HTTPS handshake |
The next two sections look at each family in turn.