md5sum - Setup

This is a discussion on md5sum - Setup ; Hi, what is md5sum? I see it in all distro cds. what is the use of it? please explain it.....

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  1. md5sum

    Hi,

    what is md5sum?

    I see it in all distro cds.

    what is the use of it?

    please explain it..

  2. Re: md5sum

    sri wrote:
    > Hi,
    >
    > what is md5sum?
    >
    > I see it in all distro cds.
    >
    > what is the use of it?
    >
    > please explain it..


    IIRC its way of taking a file and giving it an almost unique value,
    based on its contents.

    So if it changes n anyway, you re bout 99% sure that the next time you
    run MD5sum against it, you will get a different answer.

    Very useful in distinguishing between two versions of a file that have
    the same name, and length, and knowing they re different.


    But why sk me? you could have type dit into google and gotten here

    http://en.wikipedia.org/wiki/Md5sum

    a lot faster.

  3. Re: md5sum

    The Natural Philosopher writes:
    > So if it changes n anyway, you re bout 99% sure that the next time you
    > run MD5sum against it, you will get a different answer.


    More like 99.99999999999999999999999% sure.
    --
    John Hasler
    john@dhh.gt.org
    Dancing Horse Hill
    Elmwood, WI USA

  4. Re: md5sum

    John Hasler wrote:
    > The Natural Philosopher writes:
    >> So if it changes n anyway, you re bout 99% sure that the next time you
    >> run MD5sum against it, you will get a different answer.

    >
    > More like 99.99999999999999999999999% sure.

    I wont quibble, but the wiki article suggests that there is a crack to
    allow corrupted fies to be padded out with the right bit pattern to pass
    a test..


  5. Re: md5sum

    On Thu, 24 Apr 2008 03:47:24 -0700, sri wrote:

    > Hi,
    >
    > what is md5sum?
    >
    > I see it in all distro cds.
    >
    > what is the use of it?
    >
    > please explain it..


    It is a utility used to generate a unique hexadecimal number, a checksum,
    of a file. It is used primarily to verify that a downloaded file is the
    exact duplicate of the original file, that is, the downloaded file has no
    errors.

    sha1sum is also another popular checksum generator.

    Stef

  6. Re: md5sum

    On Thu, 24 Apr 2008 15:44:24 +0100, The Natural Philosopher wrote:

    > I wont quibble, but the wiki article suggests that there is a crack to
    > allow corrupted fies to be padded out with the right bit pattern to pass
    > a test..


    Obviously, You did not read the lines: "It is important to note that the
    hash value shared by the two different files is a result of the collision
    construction process. We cannot target a given hash value, and produce a
    (meaningful) input bit string hashing to that given value"

    http://www.win.tue.nl/hashclash/SoftIntCodeSign/


    --
    Regards/mvh Joachim Mæland

    If everything seems under control, you're just not going fast enough.
    -Mario Andretti

  7. Re: md5sum

    sri wrote:
    > Hi,
    >
    > what is md5sum?
    >
    > I see it in all distro cds.
    >
    > what is the use of it?
    >
    > please explain it..


    If you download a file, you can compute it's md5sum and check it against
    a stored md5sum. If the sum changed you know something has gone wrong.
    e.g. bad download, mitm or what so ever.

    cheers

  8. Re: md5sum

    sri wrote:

    > Hi,
    >
    > what is md5sum?
    >
    > I see it in all distro cds.
    >
    > what is the use of it?
    >
    > please explain it..



    New to internet too?


    http://en.wikipedia.org/wiki/MD5

  9. Re: md5sum

    liv.taylor@fredastaire.ch writes:

    >sri wrote:
    >> Hi,
    >>
    >> what is md5sum?
    >>
    >> I see it in all distro cds.
    >>
    >> what is the use of it?
    >>
    >> please explain it..


    To expand. md5 is a hash algorithm. It takes the whole file and computes
    from that a 16 byte result. That computation is designed so that if a single bit
    in the file is changed, that result is totally different( on average 1/2 of
    the bits in the result will have changed due to a single bit change in the
    file). Thus, if you calculate the md5sum of a transfered file and that of
    the original, if they are the same, you have high confidence that the two
    files are identical. If the md5 sums are different, you have certainty that
    the two files differ in at least one bit. Unfortunately it gives no clue as
    to which bits differ. You just know that the two files are different.

    It is used to ensure that the file you have is identical to the file the
    distro wanted to deliver to you.



    >If you download a file, you can compute it's md5sum and check it against
    >a stored md5sum. If the sum changed you know something has gone wrong.
    >e.g. bad download, mitm or what so ever.


    >cheers


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