1.3.1 Exchanging Data Flashcards
What is Lossless compression
An algorithm that reduces storage space needed without any loss of information
What is Lossy Compression
An algorithm that reduces storage space needed, but data is lost in the progress
What is Run Length Encoding? (2 points)
Lossless compression that reduces files size by identifying repeating series of characters.
Reduces file size where there are repeated values in a row
When is run length encoding not suitable to use?
When there is low repetition as it won’t be able to reduce file size.
What is Dictionary coding?
Reduces file size by identifying repeated patterns and replacing them with a reference to the dictionary
What is the process of dictionary coding?
Look at any sequence of words
Outputs:
-Dictionary of keys and compressed words
-Compressed version of text with references to the dictionary
What is Symmetric key encryption?
The same key is used to encrypt and decrypt
data.
What is Asymmetric key encryption?
One key encrypts data, while a different key
decrypts it.
When should you use Symmetric key encryption?
Best when only one (or few) users involved.
* e.g. backing up data.
* e.g. private storage of encrypted files.
Why should you use Asymmetric key encryption?
More secure
* Allows encryption of web traffic.
* e.g. HTTPS, password checks, card payments.
What is hashing and what is it used for?
A result gained by applying an algorithm to a
value.
* Used for generating predictable indexes for
data.
* Used as a type of one way encryption.
What is rehashing?
The process of resolving data collisions by
selecting where to put clashing data.
State the 3 types of rehashing and how they work
- Linear: move to the next available space.
- Chaining: use a linked list.
- Overflow: designate an area for rehashes.
What is Salt?
Data added to a hash to ensure every output is unique
