New PB

README.md

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 # COMP6441-birthday-attack
 
-Birthday attack demo for COMP6441: https://webcms3.cse.unsw.edu.au/COMP6441/24T3/resources/103020
+Birthday attack demo for COMP6441: https://webcms3.cse.unsw.edu.au/COMP6441/24T3/resources/103020
+
+Current PB: last 10
+Known best: last 12

confession_fake.txt

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+This is the secret confession of Richard Buckland
+to be revealed by anonymous email if I should
+mysteriously vanish.  I have left the last few hex
+digits of the SHA256 hash of this message with my
+trusted solicitor, Dennis Denuto, which will verify
+that this is indeed my intended and unaltered
+confession written by me Richard Buckland.
+
+Dennis has not seen this confession he has only seen
+the last few digits of the hash.  I have also sent copies
+of the last few digits to my bank manager and to my priest
+Father Brown.
+
+On the 10th of February I saw Mark Zukerberg near my
+house and we struck up a conversation.  He explained all
+the things he was doing to ensure that Facebook respects
+privacy - both of its users and of others.  It was very
+impressive.
+
+I feel awful that I have been criticising Facebook publicly
+for so long.  I apologised to him in our conversation and
+now I want to confess to the world that actually Facebook
+has more than enough privacy features, and that the reason
+I spend so much time criticising Facebook is that I am
+envious of Mark and wish I was a clever and smart and wise
+as he is.  I feel so bad for having been so mean to him for
+so many years that I am considering retreating to the outback.
+I may well cut off all contact with the world and live as a
+hermit from now on.  So do not worry if I vanish it is just
+that I feel so guilty that I have been so unfair to Facebook.

confession_fake.txt.out

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+This is the secret confession of Richard Buckland 
+to be revealed by anonymous email if I should
+mysteriously vanish.  I have left the last few hex 
+digits of the SHA256 hash of this message with my
+trusted solicitor, Dennis Denuto, which will verify
+that this is indeed my intended and unaltered 
+confession written by me Richard Buckland.
+
+Dennis has not seen this confession he has only seen 
+the last few digits of the hash.  I have also sent copies 
+of the last few digits to my bank manager and to my priest
+Father Brown.
+ 
+On the 10th of February I saw Mark Zukerberg near my 
+house and we struck up a conversation.  He explained all
+the things he was doing to ensure that Facebook respects
+privacy - both of its users and of others.  It was very
+impressive. 
+ 
+I feel awful that I have been criticising Facebook publicly
+for so long.  I apologised to him in our conversation and
+now I want to confess to the world that actually Facebook
+has more than enough privacy features, and that the reason
+I spend so much time criticising Facebook is that I am
+envious of Mark and wish I was a clever and smart and wise
+as he is.  I feel so bad for having been so mean to him for
+so many years that I am considering retreating to the outback.
+I may well cut off all contact with the world and live as a
+hermit from now on.  So do not worry if I vanish it is just
+that I feel so guilty that I have been so unfair to Facebook.

confession_real.txt

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+This is the secret confession of Richard Buckland
+to be revealed by anonymous email if I should
+mysteriously vanish.  I have left the last few hex
+digits of the SHA256 hash of this message with my
+trusted solicitor, Dennis Denuto, which will verify
+that this is indeed my intended and unaltered
+confession written by me Richard Buckland.
+
+Dennis has not seen this confession he has only seen
+the last few digits of the hash.  I have also sent copies
+of the last few digits to my bank manager and to my priest
+Father Brown.
+
+On the 10th of February I saw Mark Zukerberg peeping
+through my window and recording my private and personal
+conversation with my friend.
+
+I confronted him and he was very embarrassed.  He
+promised to pay me $1 million a year if I would stay
+silent and not tell anyone I had seen him do this.  I
+agreed but now I worry that it would be cheaper for him
+to make me vanish than to keep paying me.

confession_real.txt.out

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+This is the secret confession of Richard Buckland 
+to be revealed by anonymous email if I should 
+mysteriously vanish.  I have left the last few hex 
+digits of the SHA256 hash of this message with my 
+trusted solicitor, Dennis Denuto, which will verify
+that this is indeed my intended and unaltered
+confession written by me Richard Buckland. 
+
+Dennis has not seen this confession he has only seen
+the last few digits of the hash.  I have also sent copies
+of the last few digits to my bank manager and to my priest
+Father Brown. 
+ 
+On the 10th of February I saw Mark Zukerberg peeping 
+through my window and recording my private and personal
+conversation with my friend. 
+
+I confronted him and he was very embarrassed.  He
+promised to pay me $1 million a year if I would stay
+silent and not tell anyone I had seen him do this.  I
+agreed but now I worry that it would be cheaper for him
+to make me vanish than to keep paying me.

enforcer.py

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+from multiprocessing import Pool
+from hashlib import sha256
+
+# Function to calculate the hash for the given modified file content
+def calculate_hash(file_lines, num_chars):
+    return sha256("\n".join(file_lines).encode()).hexdigest()[-num_chars:]
+
+# Function to generate a modified file by adding spaces based on the bit pattern
+def modify_and_hash(args):
+    real_og, fake_og, num_chars, bit_pattern = args
+    
+    # Modify the real and fake files based on the bit pattern
+    real_modified = [
+        line + " " * ((bit_pattern >> idx) & 1)
+        for idx, line in enumerate(real_og)
+    ]
+    fake_modified = [
+        line + " " * ((bit_pattern >> idx) & 1)
+        for idx, line in enumerate(fake_og)
+    ]
+    
+    # Calculate hashes for both modified files
+    real_hash = calculate_hash(real_modified, num_chars)
+    fake_hash = calculate_hash(fake_modified, num_chars)
+    
+    return (real_hash, fake_hash, real_modified, fake_modified)
+
+def main(real_file, fake_file, num_chars):
+    # Read the original files
+    with open(real_file) as f:
+        real_og = f.read().splitlines()
+    with open(fake_file) as f:
+        fake_og = f.read().splitlines()
+
+    all_real_hashes = {}
+    all_fake_hashes = {}
+
+    found_collision = False
+
+    # Use multiprocessing Pool
+    with Pool() as pool:
+        i = 0
+        while not found_collision:
+            # Prepare a batch of bit patterns to process in parallel
+            batch_size = 100  # Number of combinations to process in parallel
+            bit_patterns = [(real_og, fake_og, num_chars, pattern) for pattern in range(i, i + batch_size)]
+            
+            # Process the batch in parallel
+            results = pool.map(modify_and_hash, bit_patterns)
+
+            # Check the results for a hash collision
+            for real_hash, fake_hash, real_modified, fake_modified in results:
+                all_real_hashes[real_hash] = real_modified
+                all_fake_hashes[fake_hash] = fake_modified
+
+                if real_hash in all_fake_hashes or fake_hash in all_real_hashes:
+                    collision_hash = real_hash if real_hash in all_fake_hashes else fake_hash
+                    print(f"Collision found! {real_file}.out and {fake_file}.out have the same hash: {collision_hash}")
+
+                    with open(f"{real_file}.out", 'w') as f_out:
+                        f_out.writelines("\n".join(all_real_hashes[collision_hash]))
+                    with open(f"{fake_file}.out", 'w') as f_out:
+                        f_out.writelines("\n".join(all_fake_hashes[collision_hash]))
+
+                    found_collision = True
+                    break
+
+            i += batch_size
+
+if __name__ == "__main__":
+    import sys
+    if len(sys.argv) != 4:
+        print(f"Usage: {sys.argv[0]} <real_file> <fake_file> <num_chars>")
+        sys.exit(1)
+
+    real_file = sys.argv[1]
+    fake_file = sys.argv[2]
+    num_chars = int(sys.argv[3])
+
+    main(real_file, fake_file, num_chars)