COMPRESION

-Reduce file size
-Maximises use of bandwidth
-Reduce download time

Reduces file size by reducing the quality (eg reducing bit depth
Suitable for images/audio and video

Uses an algorithm to reduce file size.
Original file can be restored
Suitable for executable files and docs

Run length encoding
Dictionary coding

Uses an index and sequence of occurence table to record data items leading to smaller file size
Suitable for text based documents

Stores the amt of pixels that have particular colours in frequency pairs
Suitable for (vector based)images

Single key is used to encrypt and decrypt a message.
Same key can be used multiple times or new key every time.

2 different keys are used. One for encryption and the other for decryption
One is made public the other private. Called KEY PAIRS

When you use your private key and their public key to send an authentic message.
To decrypt this they'd need to use their private key and your public key

You know no one else can read your message
They know no one else can read your message
Message becomes authentic
You know message can't be modified

Converts characters into a specific value representing original value.
Its a one way PROCESS.