From b1e2526fbb1659621ecbaf3368e8c2c9a56ff976 Mon Sep 17 00:00:00 2001
From: shockrah <alejandros714@protonmail.com>
Date: Thu, 19 Sep 2019 00:12:58 -0700
Subject: [PATCH] writing things down to never see this class again

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+# Block Ciphers
+
+The main concept here is twofold :
+
+* we take _blocks_ of data and cipher the _blocks_
+* A given key is actually used to generate recursive keys to be further used on the data itself
+
+
+_bs example ahead_
+
+Say we have a key 7 and some data 123456.
+We take the whole data set and chunk it into blocks(for example): 12 34 56.
+
+Let's say our function here is to just add 7 to each block so we do the first step: 
+
+```
+12 + 7 = 19
+Unlike other ciphers we don't reuse 7; instead we use the new thing as both the new key and part of our cipher text
+
+19 + 34 = 53
+Cipher: 1953..
+
+53 + 56 = 109 <= let's pretend that this rolls over 99 and back to 00
+          09  <= like this
+
+Final cipher: 195309
+```
+
+_It should be noted that in practice these functions usually take in huge keys and blocks_.
+
+# Feistal Cipher
+
+Two main components:
+
+1. each _thing_ in the data to cipher is replaced by a _ciphered thing_
+
+2. nothing is added or deleted or replaced in sequence, instead the order of _things_ is changed.
+
+Basically imagine that every _type of thing_ in our data maps to some other _type of thing/thing_ in the data and thus become swapped/reordered.
+
+# DES - Data Encryption Standard
+
+Widely used until about 2001 when AES surpassed it as the newer(ish(kinda)) standard.
+
+DEA was the actual algorithm tho:
+
+* 64 bit blocks
+* 56 bit keys
+* turns a 64-bit input into a 64-bit output (wew)
+* Steps in reverse also reverse the encryption itself