6 (1500U40-1) © WJEC CBAC Ltd. 12. (a) Explain what is meant by a distributed system and describe what will be distributed in the system. [2] (b) A car manufacturer has a number of dealerships across the UK. Car owners take their cars for servicing each year to a convenient dealership. Records are kept of servicing, any faults found, and replacement parts fitted. Explain the advantages to the company of implementing a distributed database system across its dealerships compared with using a single centralised database. [4] 13. (a) Explain the advantages and disadvantages of single key (symmetric) encryption compared with double key (asymmetric) encryption, giving an example, for each method, of a situation where that method would be the most suitable. [6] (b) Text is stored in 8-bit binary ASCII format, with numeric codes representing each character: A = 6510 0100 00012 B = 6610 0100 00102 C = 6710 0100 00112 The text is encrypted using a sequential XOR method: • The first character is encrypted by XOR with the key value 0110 10102 • The second character is encrypted by XOR with the encrypted value of the first character • The third character is encrypted by XOR with the encrypted value of the second character Using this algorithm, encrypt the word CAB. [3] 14. (a) Identify two hardware devices required to make a wireless connection to a network. [2] (b) State two protocols used for wireless digital communication. [2] (c) Describe one disadvantage of using a public wireless network. [2] 15. Information and advice on medical and health issues are readily available to the public through the internet, including online expert systems. Discuss the possible effects of using the internet for this purpose on health professionals and the wider community. [9] END OF PAPER (1500U40-1) 7 © WJEC CBAC Ltd. BLANK PAGE