1.3.1 Compression, Encryption and Hashing Flashcards
Define lossy compression?
Lossy compression reduces the file size by disregarding some of the information
Name a advantage lossy compression?
Lossy compression reduces the size of the file by a large amount
Name a disadvantage lossy compression?
Some of the data is lost
Define lossless compression?
Lossless compression reduces the file size but original file can be recovered
Name a advantage lossless compression?
Reduces the size of the file, the original data can be recovered
Name a disadvantage lossy compression?
Larger files than if you were to use lossy compression
Name 2 examples of lossless compression?
Run Length Encoding
Dictionary Encoding
Define RLE ( Run Length Encoding)?
Repeated data is removed and replaced with the value and the number of occurrences
Dictionary EncodingDefine RLE ( Run Length Encoding)?
Where is lossy compression typically used?
Videos
Audio
Define symmetric encryption?
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
Name a disadvantage of symmetric encryption?
If the private key is intercepted all of the communications can be intercepted and decrypted using the key
Define Caesar shift encryption?
Caesar cipher shifts the letters in the alphabet to the right by a given number of characters. (Parameter being the Key)
Name an advantage of Caesar shift?
The cipher is simple and easy to understand
Name a disadvantage of Caesar shift?
There are only 26 possibilities meaning it is very easy to crack
Define XOR encryption?
An XOR encryption is carried out between the binary value of the first character of the plain text and the key (one-time pad)
Name an advantage of XOR shift?
It is theoretically un-hackable as long as the one-time pad isn’t used more than once.
Name a disadvantage of XOR shift?
If the one-time pad is compromised then the message can be reversed
Define asymmetric encryption?
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
Name an advantage of asymmetric encryption ?
It is one of the most secure methods of encryption
Name a disadvantage of asymmetric encryption ?
It is a slow process
Define hashing?
A hashing function is when an input is turned into a fixed size value, it can’t be reversed
What 3 things are needed for a hashing algorithm to be good?
low chance of collision
be quick to calculate
and provide a smaller output then input
Dictionary Encoding
