1.3.1 Compression, Encryption and Hashing

Question 1

Define lossy compression?

Answer 1

Lossy compression reduces the file size by disregarding some of the information

Question 2

Name a advantage lossy compression?

Answer 2

Lossy compression reduces the size of the file by a large amount

Question 3

Name a disadvantage lossy compression?

Answer 3

Some of the data is lost

Question 4

Define lossless compression?

Answer 4

Lossless compression reduces the file size but original file can be recovered

Question 5

Name a advantage lossless compression?

Answer 5

Reduces the size of the file, the original data can be recovered

Question 6

Name a disadvantage lossy compression?

Answer 6

Larger files than if you were to use lossy compression

Question 7

Name 2 examples of lossless compression?

Answer 7

Run Length Encoding
Dictionary Encoding

Question 8

Define RLE ( Run Length Encoding)?

Answer 8

Repeated data is removed and replaced with the value and the number of occurrences

Question 9

Dictionary EncodingDefine RLE ( Run Length Encoding)?

Question 10

Where is lossy compression typically used?

Answer 10

Videos
Audio

Question 11

Define symmetric encryption?

Answer 11

The sender and the receiver share the same private key
The key is shared in a key exchange, this key is both used for encryption and decryption

Question 12

Name a disadvantage of symmetric encryption?

Answer 12

If the private key is intercepted all of the communications can be intercepted and decrypted using the key

Question 13

Define Caesar shift encryption?

Answer 13

Caesar cipher shifts the letters in the alphabet to the right by a given number of characters. (Parameter being the Key)

Question 14

Name an advantage of Caesar shift?

Answer 14

The cipher is simple and easy to understand

Question 15

Name a disadvantage of Caesar shift?

Answer 15

There are only 26 possibilities meaning it is very easy to crack

Question 16

Define XOR encryption?

Answer 16

An XOR encryption is carried out between the binary value of the first character of the plain text and the key (one-time pad)

Question 17

Name an advantage of XOR shift?

Answer 17

It is theoretically un-hackable as long as the one-time pad isn’t used more than once.

Question 18

Name a disadvantage of XOR shift?

Answer 18

If the one-time pad is compromised then the message can be reversed

Question 19

Define asymmetric encryption?

Answer 19

Two keys are used public key and a private key
The public key can be published anywhere, the private key is kept secret
These form a key pair and are mathematically related to each other
A single key cannot be used to encrypt and decrypt it can be encrypted with the recipient’s public key and decrypted with its private key
The message can only be decrypted by you

Question 20

Name an advantage of asymmetric encryption ?

Answer 20

It is one of the most secure methods of encryption

Question 21

Name a disadvantage of asymmetric encryption ?

Answer 21

It is a slow process

Question 22

Define hashing?

Answer 22

A hashing function is when an input is turned into a fixed size value, it can’t be reversed

Question 23

What 3 things are needed for a hashing algorithm to be good?

Answer 23

low chance of collision
be quick to calculate
and provide a smaller output then input

Question 24

Dictionary Encoding