Chapter 8: Security

Feb 28, 2020

Overview of the chapter:

8.1 Data Privacy2
8.2 Data Security3
8.3 Data Integrity4

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8.1 Data Privacy

Data Privacy: Keep the data to be available only to authorized users
-> See more in Chapter 9: Ethics

Ways to authenticate the user:

  1. Password
  2. Biometric Methods
  3. Tokens

There are also other tips to adhere:

  1. Never leave computer running while not attended
  2. Don’t write down details of accessing the computer.

8.2 Data Security

Data Security: A requirement for data to be recoverable if lost or corrupted.

Threats to data security

1. Hardware FailureNatural disasters1. Backup
* Regular Full backup, kept attest 2 generations
* Regular Incremental backups
* Record system changes during intervals between backups.

2. Alternative system – e.g. RAID

Systems running in parallel.
2. Unauthorized accessHacker1. Encryption to files

2. Set access levels

e.g. Read only access
3. MalwareVirus entering the system1. Firewall
Examines all data in and out of system.

2. Virus Checker
3. Digital Signiture

8.3 Data Integrity

Data Integrity: A requirement for data to be accurate and up-to-date

Ways ensuring data integrity:

8.3.1 For users:

The mark scheme.


Checks the format of data entered is correct, that if data matches a certain criteria. Does not confirm content.

Ways of verification:

  • Presence Check (Not NULL)
  • Format Check (Must DD-MM-YY)
  • Length Check (4-digit student num)
  • Type Check (int expected)
  • Range Check (A1 student num <=5200)


Prevents error when data is copied form one medium to another. Does not confirm content.

Common used method: Double entry, visual double-checks.

8.3.2 During Transmissions:

Parity Check

Make sure that no bit-changes occurred during transmission.

A parity bit is appended at the end to match the protocol, for example:

If agreed on even parity, there should be even number of '1's in a bit.

       Parity Bit Appended
1 1 1 1 0 0 1 [1] Is correctly transmitted.
1 1 1 1 0 0 0 [1] Is incorrectly transmitted, since there is odd (5) number of 1s.


Each bit is regarded as a binary number following a algorithm. The sum of all bits are transmitted with original data.

Same algorithm is run by the receiver. His sum is compared with transmitted sum. If they are no match then there is a data corruption.

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