1.3.1

Question 1

lossy compression

Answer 1

compresses files more than lossless but loses some of the quality and can not get it back usually by removing non essential information

e.g. gets rid of frequencies we can’t hear
can’t be used on text files because losing even 1 letter could cause issues

Question 2

lossless compression

Answer 2

doesn’t compress the file size as much as lossy but doesn’t lose any of the quality after it has been compressed by recording patterns rather than removing data

e.g. looking for common words in a text file or blocks of colour in photos

Question 3

Run Length Encoding

Answer 3

records the number of times something repeats
Not just for photos but works best especially with small colour palettes

Question 4

Dictionary based Compression

Answer 4

If certain words appear multiple times in text it is used e.g. the can be replaced with 000 which will save lots of space (dictionary will take up extra space so weigh up)

Question 5

symmetric encryption

Answer 5

also known as a private key - same key to encrypt and decrypt

Question 6

asymmetric encryption

Answer 6

uses 2 separate but related keys (public and private)
public - the person who sent you the data uses it
private - you use the key to decrypt the data

Question 7

hashing

Answer 7

its irreversible and impossible to crack in most cases unless you try all possibilities used for encrypted pins and passwords so hackers can’t read them - the hash function compares the users input and the one stored