feat: ex a2d

.gitignore

@@ -1 +1,3 @@
 *.pdf
+sheet01/a2/Hash.java
+*.class

sheet01/a2/b-sha3.txt

@@ -0,0 +1 @@
+SHA3-256 (plaintext.txt) = 8cdcfd9d0414adbba1bb146c214e181d7e5d7c8edde90b79dcb27df005fcc298

sheet01/a2/b.txt

@@ -1,2 +1,4 @@
-plaintext.txt -Algorithm SHA256
+cksum -a sha2 --length 256 plaintext.txt > b-sha2.txt
-reads the plaintext file and calculates a unique hash string using the SHA-256 cryptographic algorithm.
+reads the plaintext file and calculates a unique hash string using the SHA2-256 cryptographic algorithm and writes it into b-sha2.txt
+cksum -a sha3 --length 256 plaintext.txt > b-sha3.txt
+reads the plaintext file and calculates a unique hash string using the SHA3-256 cryptographic algorithm and writes it into b-sha3.txt

sheet01/a2/c-hash.txt

@@ -0,0 +1 @@
+03087115

sheet01/a2/c.txt

@@ -0,0 +1,3 @@
+javac Hash.java  (Compiles the java class)
+java Hash plaintext.txt  (runs the custom Hash function on the text file)
+    Output: 03087115

sheet01/a2/d.txt

@@ -0,0 +1,29 @@
+The custom hash is adding the unicode values of each character, the amount of rows and the amount of characters each multiplied with a hex value.
+This leads to it giving the same output when switching around rows, or even putting all characters into one line and adding the required amount of empty lines behind that. 
+
+
+"""
+LJVeuiolknitaaornrdia
+
+
+"""
+
+is producing the same hash as
+
+"""
+Leonard
+Viktoria
+Julian
+"""
+
+and the same as
+
+"""
+Julian
+Leonard
+Viktoria
+"""
+
+It has a good enough "first pre-image resistance" since it is not really possible to find the correct characters in the same order from the hash value that give the same original file
+The "second pre-image resistance" is weak since you can easily calculate a different file which gives the same output.
+It has no collision resistance since you can just switch around characters and get the same hash.