MD5 Collision with CRC32 Preimage

https://gist.github.com/DavidBuchanan314/a15e93eeaaad977a0fec3a6232c0b8ae

by Retr0id • 4 years ago

34 12 4 years ago

gist.github.com

eimrine• 4 years ago

MD5 is broken so badly that this hash starts and ends with 1337. Next step is to generate that type of quine when image has two pieces of string data: one is hash of image with no quine and another is exactly same image with two hashes.

londons_explore• 4 years ago

What are you talking about?? The hash does not start 1337... The hash of the example files is f54e7363d9c72ebf81605e2b38fa2be5. The crc32 is deadbeef.

Retr0id• 4 years ago

They're describing the PNG hashquine, which is referenced near the start of the article.

pxx• 4 years ago

0x1337 is only two bytes. 2^32, for four bytes, is not a particularly large number.

dmitrygr• 4 years ago

1 out of every 4 billion random files will have an md5 that matches your description. Same for sha1, sha256, sha512, and any other proper hash function...

Any proper hash function guarantees that any given bit of the output has an equal chance of being a 1 or a 0 for a random input. So for a specific pattern in 32 specific bits, there is a 1/2^32 chance in any hash func

hkopp• 4 years ago

Note that hashquines, i.e., programs that print their own hash when executed do not depend on the hash function being broken. In fact, they are a fun little exercise.

smegsicle• 4 years ago

    #!/bin/sh
    md5sum $0

acchow• 4 years ago

I have no idea where to even begin if the digest does not leak something about the data

adastra22• 4 years ago

Any cryptographic digest is not supposed to leak anything about the data that went in. That’s a core property.

In this case the hash doesn’t depend on the data at all. Do you see how that helps?

10000truths• 4 years ago

  #!/bin/sh
  HASH=6ce1c11751e405291eac368af96de90f
  # Increment until hash of this file equals $HASH: 1
  echo $HASH

a1369209993• 4 years ago

The same way as a normal quine:

  $ cat >a.py
  #! /bin/python
  import hashlib
  s='#! /bin/python\nimport hashlib\ns=%r\nprint hashlib.sha512(s%%s).hexdigest()\n'
  print hashlib.sha512(s%s).hexdigest()
  $ python a.py
  cf1daf466a7a95b245eab685b808fb861dab9af26078250a8041c4c08a8ff384 (edit: wrap)
  7f7d1853f9d62d6b40cc53d0c5be3efd80eb09f57b71250910c0d6157b73fcd3
  $ sha512sum a.py
  cf1daf466a7a95b245eab685b808fb861dab9af26078250a8041c4c08a8ff384 (edit: wrap)
  7f7d1853f9d62d6b40cc53d0c5be3efd80eb09f57b71250910c0d6157b73fcd3  a.py

MD5 Collision with CRC32 Preimage

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