GCSE OCR Computer Science Identifying & Preventing Threats to Computer Systems & Networks: Hamish needs his computer to be

Question

Hamish needs his computer to be secure from unauthorised access to his laptop.

(i) Describe the problems that can arise from unauthorised access to his laptop and confidential documents.

If unauthorised access occurs, Hamish could face several problems:

- **Data Theft**: Sensitive or confidential documents could be stolen, leading to the exposure of personal or business information.
- **Data Manipulation**: An intruder could alter or delete files, affecting the integrity of the data.
- **Malware Installation**: Hackers could install malicious software, compromising the security of the system and potentially affecting other connected devices.

(ii) Describe two ways Hamish can help prevent unauthorised access to his laptop.

1. **Strong Passwords**: Hamish should use strong, unique passwords for his laptop and accounts, making it difficult for unauthorized users to gain access.

2. **Encryption**: By encrypting sensitive files, even if an intruder gains access to the laptop, they would not be able to read the contents of the encrypted documents without the decryption key.

(b) If unauthorised access does occur, Hamish would like to use encryption to add another layer of protection to his documents.

(i) Explain how encryption helps to protect Hamish's documents.

Encryption enhances data security by converting readable information into coded texts that can only be accessed by authorized personnel with the appropriate decryption key. This means that even if unauthorized parties access the documents, they will be unable to interpret the data without the key.

(ii) One encryption method is a Caesar cipher.

This Caesar cipher moves each letter of the alphabet one place to the right.
For example, if the message read: HELLO, this would be stored as: IFMMP.

The following pseudocode algorithm takes a string of uppercase letters as input and uses the Caesar cipher to encrypt them.

```
01 message = input("Please enter your string")
02 newMessage = ""
03 messageLength = message.length
04 for count = 0 to messageLength - 1 do
05 	 ASCIIValue = ASC(message.subString(count,1))
06 	 ASCIIValue = ASCIIValue + 1
07 	 if ASCIIValue > 90 then
08 	 	 ASCIIValue = ASCIIValue - 26
09 	 end if
10 	 newMessage = newMessage + CHR(ASCIIValue)
11 next count
```

(iii) The algorithm needs adapting. An extra line (line 12) is needed to output the encrypted message.

Write line 12 to output the encrypted message in pseudocode or programming code.

12 print(newMessage)

Hamish needs his computer to be secure from unauthorised access to his laptop - OCR - GCSE Computer Science - Question 3 - 2019 - Paper 1

Worked Solution & Example Answer:Hamish needs his computer to be secure from unauthorised access to his laptop - OCR - GCSE Computer Science - Question 3 - 2019 - Paper 1

Describe the problems that can arise from unauthorised access to his laptop and confidential documents.

Describe two ways Hamish can help prevent unauthorised access to his laptop.

Explain how encryption helps to protect Hamish's documents.

Complete the pseudocode algorithm to perform a Caesar cipher.

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