Hashing and Compression

Compression

• Reduce size of files

• Reduce download times

• Reduce storage requirements

• Make best use of bandwidth

• Reduce transmit times

Lossy Compression

• Used for images, audio and video

• Unnoticeable reduction in quality

• Canot be restored to original

• Permanently deletes part of the file

Lossless Compression

• Fully able to restore the image to original quality when uncompressed

• Only useful on images with large areas of continuous colours

• Useful for vector-like images

• Used for executable files and documents

Hashing

Transforms a string of characters into a fixed length value that represents the original input string

Popular choices are SHA-1 and MD5

It is a one-way process; you cannot set original value from hashed value even if you have access to the original hashing algorithm

Ideal for preventing passwords and PINs being read by a hacker (and understanding it)

To verify the user’s password; the system needs to:

• Apply hashing factor to password entered

• Compare hashed value to the one stored

Can be used for quick searching, insertion, deletion of data