did part 4

part4/4a.py

@@ -0,0 +1,34 @@
+import string
+import random
+import hashlib
+
+letters = string.ascii_lowercase + string.ascii_uppercase
+
+# 4a
+
+def H(m: str) -> str:
+    return hashlib.sha256(m.encode()).hexdigest()[:2]
+
+i = 0
+hashes = []
+messages = []
+while True:
+
+    n_char = random.randint(1, 1000)
+    m = ''.join([random.choice(letters) for n in range(n_char)])
+    hm = H(m)
+
+    # print(i)
+    # print(m)
+    # print(hm)
+
+    if hm in hashes:
+        print(f'Message 1 "{m}" and message 2 "{messages[hashes.index(hm)]}" have the same hash {hm}.')
+        print(f'It took {i} iterations to find a collision.')
+        break
+    else:
+        hashes.append(hm)
+        messages.append(m)
+
+    i += 1
+

part4/4b.py

@@ -0,0 +1,37 @@
+import string
+import random
+import hashlib
+
+letters = string.ascii_lowercase + string.ascii_uppercase
+
+# 4a
+
+def H(m: str) -> str:
+    return hashlib.sha256(m.encode()).hexdigest()[:2]
+
+
+counts = []
+for n in range(20):
+    i = 0
+    hashes = []
+    messages = []
+    while True:
+
+        n_char = random.randint(1, 1000)
+        m = ''.join([random.choice(letters) for n in range(n_char)])
+        hm = H(m)
+
+        # print(i)
+        # print(m)
+        # print(hm)
+
+        if hm in hashes:
+            counts.append(i)
+            break
+        else:
+            hashes.append(hm)
+            messages.append(m)
+
+        i += 1
+
+print(f'Average number of trials for a collision: {sum(counts)/len(counts)}')