IGCSE Computer Science Paper 1 Definitions Worksheet: 2.2 Methods of Error Detection and 2.3 Encryption (Modules 189–203)
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Key terms
Write what each term means, in your own words.
1
Choosing a method
2
interception
3
plaintext
4
ciphertext
5
encryption key
6
unreadable without the key
7
symmetric encryption
8
shared secret key
9
key interception
10
public key
Answer Key
IGCSE Computer Science Paper 1 · Modules 189–203 · Student wording will vary for definitions
1Choosing a method — Decide if the error happens in transmission or data entry, pick the check that fits, then justify it by what it can and cannot detect.
2interception — When someone copies data as it travels across a network through routers and other devices, so unprotected data can be read by anyone who intercepts it, for example on public Wi-Fi.
3plaintext — The original, readable data (text, file, image or message) before it is encrypted. Decrypting ciphertext with the correct key turns it back into plaintext.
4ciphertext — The scrambled, unreadable data made when plaintext is encrypted. It is what gets sent across a network and looks meaningless without the key.
5encryption key — A secret value used by the encryption algorithm to scramble data into ciphertext and unscramble it again. A different key gives different ciphertext, and a longer key is harder to guess.
6unreadable without the key — Encryption cannot stop data being intercepted, but the interceptor sees only ciphertext and cannot get the plaintext without the key, so passwords and bank details stay safe.
7symmetric encryption — The sender encrypts plaintext into ciphertext with a key; the receiver decrypts it back to plaintext using the same key. A wrong key gives unreadable output.
8shared secret key — In symmetric encryption, the receiver can only decrypt if they hold the same key as the sender, so the key must be shared before any data is sent.
9key interception — If an attacker intercepts a symmetric key while it is being shared, they can decrypt every message that uses that key, so the encryption is defeated.
10public key — The half of a key pair that the owner shares openly. Anyone can use it to encrypt data sent to the owner, but it cannot decrypt that data. Only the matching private key can.