Compression, Encryption & Hashing (OCR A Level Computer Science): Exam Questions

A hotel stores data about rooms, customers and bookings in a database. Each customer can book multiple rooms and each room can be booked multiple times.

Describe two different ways that hashing could be used in this database.

A team of programmers create a robot that will be used in a factory. The robot will be able to do the work of multiple humans.

The programmers discuss whether to write the instructions for the robot in assembly language or a high-level language.

The robot stores data internally and also communicates with other robots and users via a wireless network which is password protected. All data for these tasks is secured using either encryption or hashing.

Compare the robot’s use of encryption and hashing for storing and communicating data

You should include the following in your answer:

• the different types of encryption that could be used and how this would secure data

• how hashing could be used to secure data and which data would be suitable

• why encryption and hashing are used by the robot for stored data and communications.

OCR Solutions is a software development company. Employees use a wide range of application software to complete admin tasks. Tasks include writing letters to clients and creating graphics.

The thin client computer needs to send data that is input by the user to the server so that the virtual machine can process it. For example, it will send text entered by the user on the thin client computer to the application software running on the virtual machine.

Data is compressed in order to improve the speed of data transmission between the client and the server.

Explain why lossless compression should be used instead of lossy compression.

A school uses a database to manage student records, teacher information and class assignments. Each student can be enrolled in multiple classes and each teacher can teach multiple classes.

Describe two different ways that hashing could be used in this database.

A hash table uses the hash function Index = Key MOD 10. The keys 24, 54, and 84 are inserted in that order.

Evaluate the impact of these keys on the performance of the hash table, referring to linear probing and chaining.

A company uses Symmetric encryption for internal backups but Asymmetric encryption to transmit sensitive data to a third party.

Evaluate why Asymmetric encryption is more secure for transmission.

An e-commerce platform uses Asymmetric encryption to establish a secure connection and Symmetric encryption for session data.

Justify this hybrid approach.

A 24-bit bitmap image contains a large block of identical blue pixels followed by a detailed landscape.

Analyse the effectiveness of RLE and Dictionary Coding.

A technical manual contains many repeated long phrases.

Evaluate whether RLE or Dictionary Coding would give better compression.