Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
I recently ran a process that produced 100 million md5s of randomly generated data. I hit duplicates in that process on at least two runs.
Are you absolutely certain that the random data itself contained no duplicates? I would be very interested to see these MD5 collisions of yours.
I think that the odds of generating 2 matching pairs from 500 million is probably well within statistical norms.
Sure. If you reduce MD5 to about 30 bits.
However, if you gave me an md5, and asked me to find a plaintext that matched it, without giving me the plaintext you had used to generate it. That would be computationally infeasible. This, I belive, is what the md5 algorithm is intended to achieve.
This is known as the Preimage Problem. It's much more difficult than the Collision Problem (finding two messages with the same MD5). Cryptographic hashes are supposed to prevent someone from doing either one. You can answer "no they aren't" again if you want, but you will still be wrong.
Alternatively, take my trojan binary and the md5 from some trusted piece of code, and then tell me what bytes I need to insert into data space (and where) within that binary in order for it's md5 to match that of the trusted piece of software. That would be a vulnerability that would make me consider md5 broken.
There are more uses of MD5 than are dreamt of in your philosophy, Horatio.

In reply to Re^7: On showing the weakness in the MD5 digest function and getting bitten by scalar context by Anonymous Monk
in thread On showing the weakness in the MD5 digest function and getting bitten by scalar context by grinder

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others exploiting the Monastery: (6)
    As of 2014-09-16 02:04 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My favorite cookbook is:










      Results (155 votes), past polls