The worth of (external) ISO check sums?

Discussion in 'Wii - Hacking' started by Wiimm, May 5, 2010.

  1. Wiimm

    Wiimm Developer

    Aug 11, 2009
    Long time ago I was asked:
    Every now and again I've been thinking about this. But what is the worth of such check sum if the partitions is modified because of scrubbing? Because of absence of clarity (for me) I have never implemented it.

    On the other hand every 1024 bytes of user data in every partition has its own SHA1 check sum (called 'H0'). There are also H1 (hash of 31*H0), H2 (hash of 8*H1), H3 (hash of 8*H2) and for the whole partition one H4 (hash of all H3) check sums. To validate a complete or a scrubbed partition it is enought to calculate the check sums and compare them with the stored sums. For a scrubbed image it is enough to compare the check sums of the used sectors. wit VERIFY does exactly this.

    And now my questions:[*]Is there really a need to calculate md5/sha1 check sums and print them out?[*]And if "yes": Why?[*]And if again "yes": Which check sums (disc|partitions, md*|sha*|crc*) are needed?
    And again: To find out bad dumps no more than the internal check sums are needed.
  2. XFlak

    XFlak Wiitired but still kicking

    Sep 12, 2009
    If the internal checksum can easily be added to apps like wii backup manager (or wii game manager) then I personally don't see the need for an external check, but I'd still like to hear the opinions of those smarter than me (like Giantpune, cwstjdenobs, etc.)
  3. tueidj

    tueidj I R Expert

    Jan 8, 2009
    There is no point, the existing partition structure already has enough information (as long as scrubbing a partition doesn't modify the H3 table).