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312/notes/ciphers.md

@@ -1,6 +1,6 @@
 # Block Ciphers
 
-The main concept here is twofold :
+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
@@ -28,6 +28,33 @@ Final cipher: 195309
 
 _It should be noted that in practice these functions usually take in huge keys and blocks_.
 
+> Deciphering
+
+Start from the back of the cipher not the front; if we used and xor function scheme (which is a symmetrical function) we would simply just xor the last block by itself and thus perform the same encryption scheme but in reverse.
+
+Example::Encryption
+
+```
+Key: 110
+Function scheme: xor
+Data: 101 001 111
+
+101 011 010
+110 001 111
+
+011 010 101 <= encrypted
+
+```
+
+Example::Decryption
+
+```
+Ciphered: 011 010 101
+Function scheme: xor
+
+...
+```
+
 # Feistal Cipher
 
 Two main components:

312/notes/public.md

@@ -0,0 +1,16 @@
+# Asymmetric Key Encryption(Public/Private)
+
+
+Think of a box that we put things inside of:(put simply) 
+
+* Private key: can open the box
+* Public key: can lock the box
+
+Caveats:
+
+Public keys contain a unique signature, which can be used to _sign_ a message. Even though everyone can open the message they also know who locked the box.
+
+Imagine then, lock the box with private key(secure) and sign it with the public key(authorized).
+
+
+