trash hash seems to work

src/calchash.py

@@ -0,0 +1,28 @@
+# this is literal garbage
+# does not even work for the bad hash
+def calcHash():
+    message = list('A' * 4)
+
+    accu = int("a5a5a5a55a5a5a5a55555555aaaaaaaa", 16)
+
+    for i in range(0, len(message)):
+        message[i] = hex(ord(message[i]))[2:]
+
+    if len(message) % 16 != 0:
+        remainder = -((len(message) % 16) - 16);
+        for i in range(0, remainder):
+            message.append("FF")
+
+    chunks = []
+
+    for i in range(0, len(message), 16):
+        chunk = "".join(message[i:i+16])
+        chunks.append(chunk)
+
+    for B in chunks:
+        accu = accu ^ int(B, 16)
+
+    print(accu)
+    return accu
+
+calcHash()

src/trash-hash.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+"""
+Dirty hash we were covered in an excercise for Week 16 of 2023 in cryptography
+"""
+import math
+import random
+
+DEFINED_INITIAL = bytearray(b'\xa5\xa5\xa5\xa5\x5a\x5a\x5a\x55\x55\x55\xaa\xaa\xaa')
+
+def trash_hash(input: bytearray) -> bytearray:
+    print("original len is %s" % len(input))
+    # extend with 0xff if length is not multiple of 16
+    while len(input) % 16 != 0:
+        input.append(0xff)
+
+    # set n
+    n: int = math.ceil(len(input)/16)
+    print("len is %s" % len(input))
+    print("n is %s" % n)
+
+    # cut input into blocks with size 16
+    blocks = [bytearray(16)] * n  # initializes with 0x00s
+    # print the empty blocks
+    #for block in blocks:
+    #    print("block: %s" % block.hex())
+    #print('='*80)
+
+    for i in range(0, n):
+        blocks[i] = input[i*16:i*16 + 16]
+
+    # print the filled blocks
+    #for block in blocks:
+    #    print("block: %s" % block.hex())
+
+    # initilaize accumulator A_0 with the following constant values:
+    A_list = [DEFINED_INITIAL] * n
+
+    # iterate over blocks
+    for index, block in enumerate(blocks):
+        if index == 0:
+            pass
+        thing = bytes(by0 ^ by1 for by0, by1 in zip(A_list[index - 1], block))
+        A_list[index] = bytearray(thing)
+        print("final thing: %s" % A_list[index])
+
+    A = bytearray(1)
+    A.pop()
+
+    return A.join(A_list)
+
+def main():
+    some_bytes = bytearray(b'AAAA');
+    print("hashed: %s" % some_bytes.hex())
+    print('='*80)
+    hashed = trash_hash(some_bytes)
+    print('='*80)
+    print("hashed: %s" % hashed.hex())
+
+if __name__ == "__main__":
+    main()