Encryption
Cambridge IGCSE Computer Science (0478) · Unit 2: Data transmission · 9 flashcards
Encryption is topic 2.3 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 2 — Data transmission , alongside Types and methods of data transmission and Error detection and correction. In one line: Encryption is the process of converting plaintext into ciphertext to protect its confidentiality. This scrambling of data prevents unauthorized access.
This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).
The deck below contains 9 flashcards — 6 definitions, 2 key concepts and 1 application card — covering the precise wording mark schemes reward. Use the 6 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
The term 'encryption'
Encryption is the process of converting plaintext into ciphertext to protect its confidentiality. This scrambling of data prevents unauthorized access.
What the Cambridge 0478 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Understand Understand the need for and purpose of encryption when transmitting data
- Understand Understand how data is encrypted using symmetric and asymmetric encryption including the use of public and private keys
Define the term 'encryption'.
Encryption is the process of converting plaintext into ciphertext to protect its confidentiality. This scrambling of data prevents unauthorized access.
Explain the purpose of 'decryption'.
Decryption is the reverse process of encryption, converting ciphertext back into readable plaintext. It requires the correct key to restore the original data.
What is a 'cipher' in the context of encryption?
A cipher is an algorithm used to perform encryption or decryption.
Differentiate between 'plaintext' and 'ciphertext'.
Plaintext is the original, unencrypted data, while ciphertext is the encrypted, unreadable form of the data after encryption. Plaintext is transformed into ciphertext.
Outline the key difference between 'symmetric' and 'asymmetric' encryption.
Symmetric encryption uses the same key for both encryption and decryption, while asymmetric encryption uses a public key for encryption and a private key for decryption. Symmetric is faster, asymmetric is more secure for key exchange.
Explain the purpose of a 'public key' in asymmetric encryption.
The public key is used to encrypt data and can be freely distributed. Anyone can use the public key to encrypt a message, but only the holder of the corresponding private key can decrypt it.
Explain the purpose of a 'private key' in asymmetric encryption.
The private key is kept secret and is used to decrypt data that was encrypted with the corresponding public key. It ensures that only the intended recipient can read the message.
Describe the role of SSL/TLS in securing online communications.
SSL/TLS (Secure Sockets Layer/Transport Layer Security) are protocols that provide secure communication over a network by encrypting data transmitted between a web server and a browser. They use a combination of symmetric and asymmetric encryption.
Explain why encryption is important for data security.
Encryption protects sensitive information from unauthorized access by rendering it unreadable. This is vital for maintaining privacy and confidentiality, especially when transmitting data over public networks.
Key Questions: Encryption
Define the term 'encryption'.
Encryption is the process of converting plaintext into ciphertext to protect its confidentiality. This scrambling of data prevents unauthorized access.
Explain the purpose of 'decryption'.
Decryption is the reverse process of encryption, converting ciphertext back into readable plaintext. It requires the correct key to restore the original data.
What is a 'cipher' in the context of encryption?
A cipher is an algorithm used to perform encryption or decryption.
Differentiate between 'plaintext' and 'ciphertext'.
Plaintext is the original, unencrypted data, while ciphertext is the encrypted, unreadable form of the data after encryption. Plaintext is transformed into ciphertext.
Explain the purpose of a 'public key' in asymmetric encryption.
The public key is used to encrypt data and can be freely distributed. Anyone can use the public key to encrypt a message, but only the holder of the corresponding private key can decrypt it.
More topics in Unit 2 — Data transmission
Encryption sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Encryption deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Encryption deck
Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.
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