State two differences between symmetric and asymmetric encryption.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

1. [1] (a) One mark for each point • Symmetric encryption uses a single key and asymmetric encryption uses a pair of keys.
2. [1] (a) • The symmetric single key is used by all, whereas only one of the keys for asymmetric encryption is available to everyone / one of the asymmetric encryption keys needs to be kept secret.
3. [1] (b) One mark for each point (Max 4) • The organisation requests a certificate from a Certificate Authority (CA)
4. [1] (b) • The organisation may send their public key to CA
5. [1] (b) • The organisation gathers all the information required by the CA in order to obtain their certificate, which includes information to prove their identity
6. [1] (b) • The CA verifies the organisation's identity
7. [1] (b) • The CA generates / issues the certificate including the organisation's public key (and other information).