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So here's my dilemma:

i ran these 3 commands in terminal, one at a time, to check the hashes of a burnt dvd:

dd if=/dev/cdrom bs=1 count='size' | md5sum

dd if=/dev/cdrom bs=1 count='size' | sha1sum

dd if=/dev/cdrom bs=1 count='size' | sha256sum

The thing is, the md5 of the burnt dvd was the same as the ISO image md5. However the sah1 and sha256 were completely different!

Questions:

  1. Are the above mentioned commands the correct ones for getting those 3 hashes?

  2. How is it possible for the md5 to match, but the sha1 and sha256 not to? Why is that? And how can i fix it?

Thank you for the upcoming support!

  • Is 'size' really some literal long number? – psusi Jan 21 '15 at 22:53
  • what do you mean literal? in my case it's 3320903680 – Zeno Jan 21 '15 at 23:02
  • Ok, yea.. just making sure you were really giving the number and just omitted it in the question instead of literally trying to pass "'size'" to dd – psusi Jan 21 '15 at 23:06
  • got it. maaan that wouldn't have made any sense :))) – Zeno Jan 21 '15 at 23:11
  • Well, if you are using the same cdrom, and the same size number each time, then it shouldn't be possible for one to agree and the other two not to. – psusi Jan 22 '15 at 1:20
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  1. the 3 terminal codes are the right ones to get the hashes. if you verify the hashes with them it is impossible for 1 hash to match and the others not to.

2.they didn't match because i used the md5 checking code correct but for the other two i used: sha1sum dev/cdrom and sha256sum dev/cdrom. I checked the dvd again with the correct terminal commands and they all matched

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