1.3.1 compression, encryption, hashing

Question 1

compression

Answer 1

it shrinks file size by removing data/ summarising data
+example

• data sent quickly (quicker downloads)
• uses fewer bandwidths for transmission(cheaper)
• less buffering (audio and videos)
• saves storage space

Question 2

lossy compression

Answer 2

Shrinks file size by PERMANENTLY removing data. Suitable for images, audio, videos.
e.g. jpg, mp3

Question 3

lossless compression

Answer 3

Shirks file size by grouping data of similar patterns. Suitable for texts and code.
e.g. png, zip files

Question 4

RLE

Answer 4

run length encoding(lossless)

Shrink file size by grouping back-to-back similar data. Suitable for simple images and sound.

Question 5

Dictionary compression

Answer 5

Stores data with repeating pattern into a dictionary, represented by binary code.

Then uses a POINTER to point the data out from the dictionary

Suitable for text files and codes(lossless compression)

Question 6

encryption

Answer 6

transformation of data so that unauthorised users cannot understand it

two way, data can be restored with key

Question 7

plain text, cipher text and key

Answer 7

plain text: original data
cipher text: encrypted data
key: deciphering

Question 8

symmetric encryption

Answer 8

uses the same key to encrypt and decrypt data

Question 9

assymmetic encryption

Answer 9

uses two separate but related keys, private key and public jkey

Question 10

hashing

Answer 10

applying an algorithm to the original data to prevent unauthorised access, cannot be reversed

Question 11

salt

Answer 11

additional piece of data to further secure the hashed value (because rainbow tables exist)