1. Lesson Objectives Aims You should know about: 1.3.1:
(d) Different uses of hashing.

2. Let’s work backwards
Some things to understand:
Encoding
Encryption
Hashing
Obfuscation

3. Obfuscation
The idea of making something difficult for a human to understand
It is NOT encryption
It is an easily reversible process
Computers can still understand it easily

4. Encoding
Encoding is the process of turning something into a binary form
Or turning data into a form that can be understood by another system
ASCII, Unicode, UTF are examples of encoding

5. Encryption
The transforming of data so that it can be kept secret/safe regardless of interception
Not designed to be easy to use!
Only specific people (key holders) can reverse the transformation

6. Generally data is encoded with private key – kept secret
Encryption
Generally data is encoded with private key – kept secret
To decrypt the data you need:
The cipher text
The algorithm
The key
Examples:
AES, Blowfish, RSA, PGP

7. Hashing
A one way mathematical function which should produce a unique output for any given input
The same input will always produce the same hash every time

8. Hash rules
The same input will always produce the same output.
Multiple disparate inputs should not produce the same output.
It should not be possible to go from the output to the input.
Any modification of a given input should result in drastic change to the hash.

9. A file can be hashed to ensure integrity
Uses
A file can be hashed to ensure integrity
If even the smallest change is made, the hash changes
Wrong hash = tampered file
Data can be hashed to make it incredibly quick to search/find elements

10. Because of its one way nature
Another use
Because of its one way nature
And the fact you shouldn’t be able to work out the input from the output…
Passwords are often hashed when stored in databases
User signs up – password is hashed using an algorithm
User signs in, password hashed, if they match then access is granted
This can lead to issues…

11. Collisions
There is no perfect hashing algorithm
It’s just incredibly unlikely that two things will produce the same output.
When this occurs, a collision has happened:

12. A stupendously good website
Read this link:
Make notes on:
Why hashes are NOT encryption
Collisions
Collision resistance
Problems with hashing
Examples of hashing algorithms (MD4, 5 etc)

13. Review/Success Criteria