Re: Complex Theoretical One Way Hash Question

Francois Grieu wrote:
> In article <e27gr8$1a2n$2@agate.berkeley.edu>,
> daw@taverner.cs.berkeley.edu (David Wagner) wrote:
>
> > The more complicated the image format, the more plausible it
> > is that there is some existing corner case functionality that
> > can be used in a strange way.
>
> It comes to me that, juste like it is feasible to make two
> different postscript files with the same MD5 and showing
> different meaningfull things
> http://www.cits.rub.de/MD5Collisions
> it is possible to make a postscript file that displays
> its own MD5: we make it contain 128 blocks that each
> can be changed to two states without changing the MD5,
> and display the 128 bits coded herein as 32 hex chars,
> on top of an image also in the (end of) of the file;
> then set the 128 blocks as approriate to display the
> MD5 of the file.
>

Since postscript is a turing complete language, couldn't you just make
it calculate the MD5 digest of itself and then print it? It would
essentially be a quine that instead of printing itself printed the MD5
digest of itself. It should be possible in any language that allows
both printing quines and calculating MD5.

   Ben
Received on Mon May 1 02:03:18 2006