Encryption is used to scramble data to make it meaningless if intercepted.

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

1. [2] One mark per mark point (Max 2) MP1 to produce a virtually unbreakable encryption system / send virtually un-hackable secure messages MP2 ...using the laws / principles of quantum mechanics / properties of photons MP3 detects eavesdropping MP4 ...because the properties of photons change MP5 to protect security of data transmitted over fibre optic cables MP6 to enable the use of longer keys.
2. [3] One mark per mark point (Max 3) MP1 Symmetric cryptography uses a single key to encrypt and decrypt messages, Asymmetric cryptography uses two. MP2 The symmetric key is shared, whereas with asymmetric, only the public key is shared (and the private key isn't). MP3 ... the risk of compromise is higher with symmetric encryption and asymmetric encryption is more secure. MP4 Symmetric cryptography is a simple process that can be carried out quickly, but asymmetric is much more complex, so slower. MP5 The length of the keys in symmetric encryption are (usually) shorter than those for asymmetric (128/256 bits v 2048 bits).