csnotes/312/hash.md

Cryptographic Hash Functions

Random Jargon

If you made it this far you know what all of this is but we need these terms because "muh academic vernacular"

• Variable Length Input
• Fixed size output

a = {
	'first',
	'second',
}

Both first & second as inputs result in distinct references of the same size.

• One-way property

You should not be able to use a hash result(i.e. reference) to find an input.

In English: Only inputs can find outputs, not the other way around.

• Two-way property/ Collision-free Property

2 identical data inputs will map to the same output

What does a hash provide?

• Integrity checks

• Message Digest / Authentication

Hashes are not secure ffs. When we say authentication we really mean that we are checking to ensure there has been no changes to the original message. NOTE: this really doesn't guarantee anything in communications susceptible to man-in-the-middle attacks.

Let's get real for minute: Think of it this way a message is like a car and the key is our hash. If the key doesn't fit in the slot then its not our car, but if we sent our car + key oversees whoever steals the car + key has full control and we lose security effectively. Using SSL is kinda like putting that car + key combo in a box that nobody except the recipient can open.