Selma has some important personal information that she needs to email to her employer. She wants to make sure that if the personal information is intercepted, it cannot be understood. State how Selma could email her personal data more securely.

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

1. [1] (a)(i) Encryption
2. [1] (a)(ii) Her personal details before encryption is the plain text
3. [1] (a)(ii) The plain text/her personal details is encrypted using an encryption algorithm
4. [1] (a)(ii) The plain text/her personal details is encrypted using a key
5. [1] (a)(ii) The encrypted text is cypher/cipher text
6. [1] (a)(ii) The key is transmitted separately (from the text)
7. [1] (a)(ii) The key is used to decrypt the cypher text (after transmission)
8. [1] (b) Checksum
9. [1] (b) Calculation carried out on data
10. [1] (b) (checksum/calculated) value sent with data
11. [1] (b) recalculated after transmission and compared to original
12. [1] (b) If they do not match an error is present
13. [1] (b) ARQ
14. [1] (b) uses acknowledgment and timeout
15. [1] (b) A request is sent with data to acknowledge all data is received
16. [1] (b) Acknowledgement sent back to say all data is received
17. [1] (b) If no acknowledgement is received in a time frame an error in transmission detected / data automatically resent.