# 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 ```python 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.