Unit 1.3.1 Compression, Encryption and Hashing

17 cards·by gurundus

What is a disadvantage of Lossy Comrpession?

The original file cannot be recovered from the compressed version as the removed data is lost

Where is lossy Compression most often used?

It is typically used for sound and video files, where the change will not necessarily be noticed.

What are some of the ways inwhich lossy compression can be used?

Sound file the compressor could clip off inaudible frequencies, or a image file could have resolution lowered or its colour range reduced

What are the two main methods for lossless compression?

Dictionary Encoding and Run Length Encoding

What is an example of a Dictionary Encoder?

Lemple-Ziv-Welch (LZW) encoder

Where is the Run Length Encoding technique found?

It is found in TIFF and BMP files

What is an advantage of lossy compression?

Lossless compression is not often as effective as lossy compression when trying to reducefile sizes

What is an advantage of lossless compression?

Lossless is the only option for files such as text files or executable programs, where any loss of data would destroy their functionality.

What are the two main types of encryption?

symmetric and asymmetric encryption

What is the advantage of using symmetric encryption?

It is very quick to encode and decode

What is the disadvantage of using symmetric encryption?

This requires both the sender and recipient to store the key safely, it is easier to crack if the key is shared

How do the other keys in asymmetric encryption work?

A single public key is known by both, but when the encryption algorithm is implemented a second compatible private key is also used.

How is the message decrypted when using asymmetric encryption?

the public key is applied alongside the private key again

What is the disadvantage of using asymmetric encryption?

It requires more processing power.

What are the two uses for hashing algorithms?

generate memory addresses for storing records in databases quickly and also used to store and check passwords

where are hashing algorithms used?

storing passwords, but not encrypting data

How are hashing algorithms used?

a user enters a password, it is hashed and stored on a server, when the user attempts to login, the hashing algorithm applied to check it.