1.3.1 Compression, Encryption and Hashing

Question 1

1.3.1 A)
Why should you use compression

Answer 1

-reduces file size
-reduces download time
-reduce storage requirments
- best use of bandwidth

Question 2

1.3.1 A)
How does compression work

Answer 2

reduces overall file size of a file as much as possible when it is reviced file needs to be uncompressed.

Question 3

1.3.1 A)
What are the two types of compression

Answer 3

lossy & lossless

Question 4

1.3.1 A)
How does lossy compression work

Answer 4

reduces file size while removing some of its infomation could result in more pixelated images or less clear audio

Question 5

1.3.1 A)
How does lossless compression work

Answer 5

reduce file size of file without losing info orginal can be revcover.

Question 6

1.3.1 B)
What is run length encoding

Answer 6

method of lossless compression. repeated values are removed and replaced with one value. May not be reduced by a big number if no repeats
AAABBC = 3A2B1C

Question 7

1.3.1 B)
What is dictionary encoding

Answer 7

Lossless compression stored alongside a dictonary example in notes.
index frequently occuring notes.
rewrite with index

Question 8

1.3.1 C)
What is encryption

Answer 8

Used to keep data secure. scrambles data before its send and then dispher once arrive.

Question 9

1.3.1 C)
What are the two types of encryption

Answer 9

Symmetric & Asymmetric

Question 10

1.3.1 C)
What is symmetric encryption

Answer 10

sender and reciever share the same priv key. Key is used for encryption and decryption

important private key is kept secret. if key is intercepted during key exhange communication can be intercepted and decryption

Question 11

1.3.1 C)
What is asymmetric encryption

Answer 11

Solves this problem of interception.
Uses two keys one priv and one public. Public key can be used/published anywhere
Two keys are key pairs they are mathematically related

A single key cannot be used to both encryption and decryption. recipent has the private key

Digital signitrues send a msg w private key.

Question 12

1.3.1 D)
What is hashing

Answer 12

Process in which an input(a key) is turned into a fixed size value (a hash) the algorthmn that does that is called hasing algroithm.

output of hashing function cannot be revered to form the key, makes it good for storing passwords.

Question 13

1.3.1 D)
What is another use for hashing

Answer 13

Hash table is a data structure which holds key-value. used to look up data in an array in constant time, for example cache and data base.

Two keys can produce the same hash which can cause collion.
To overcome collison store items together in a list under hash value or use a second hash function to make a new hash

A good hash function should have low collision chance and should produce an output which is smaller than the input it was provided otherwise it would be quicker to simple serch for the key.

Question 14

1.3.1 C
Two characteristic you want from a hashing algorithm

Answer 14

Low Collision rate
Provides a smaller output than input
(This is the last point of flash card 13 but I want to make it clearer)