Encryption: symmetric and asymmetric
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 3 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A message anyone could read
- What encryption does
- Three key words
Read the transcript of the teaching part
Last time
Before we start: last time, in Checksum, echo check, ARQ and check digits, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
A message anyone could read
Every packet you send passes through many routers you do not own. Anyone along the way could intercept it and read it. Encryption is the answer: it scrambles the data so it means nothing to them.
What encryption does
Encryption scrambles data so that, if it is intercepted, it cannot be understood. It does not stop the data being intercepted. It only makes it meaningless to anyone without the key. Only someone with the right key can turn it back.
Three key words
Plaintext is the original data, before encryption. Ciphertext is the scrambled data, after encryption. An encryption key is a value, such as a string of characters, used by the algorithm to encrypt and decrypt the data.
How often it comes up
The whole chapter: Encryption.
Chapter 2.4: Encryption
- Encryption: symmetric and asymmetric 4 min
Also for IGCSE Computer Science 0478
Which topics come up most in IGCSE Computer Science 0478 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.