Encryption is used to alter data into a form that makes 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] (a) One mark per mark point (Max 2) MP1 To provide better security MP2 by using two different keys / a public key and a private key MP3 One of the keys is used to encrypt the message MP4 the matching key is used to decrypt the message.
2. [4] (b) One mark per benefit (Max 2) MP1 Provides security based on laws of physics rather than mathematical algorithms, so more secure. MP2 To protect the security of data transmitted over fibre optic cables. MP3 Virtually unhackable. MP4 The performance of quantum cryptography is continuously improved, making it suitable for most valuable government/industrial secrets. MP5 Longer keys can be used MP6 Eavesdropping can be detected One mark per drawback (Max 2) MP1 Lacks many vital features such as digital signature, certified mail, etc. MP2 High cost of purchasing / maintaining equipment required. MP3 Currently only works over relatively short distances. MP4 Error rates are relatively high as technology is still being developed. MP5 Polarisation of light can change during transmission. MP6 Allows criminals and terrorists to hide their communications.