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All we know from there is that your image is different than the "official" ones on the Ubuntu servers. Yours didn't match and produced a completely different string. In a case of a mismatch, several things could have caused it: download from an untrusted source, unreliable network connection, local file system corruption, etc. If it matches, then both files are exactly the same 1 and you're all set. You can check the integrity of your copy by running the same checksum and verify it is the same as Ubuntu has published.
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For each file available, Ubuntu publishes SHA1, SHA256 and MD5 checksums (available on your favourite mirror, e.g. Ubuntu installation media are large sets of downloads. In the meantime, just re-download it from a reliable source and check it using md5sum after download against the list of published hashes here: Ubuntu community wiki - UbuntuHashes.
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We've determined that from the comments - here's the how and why. Your ISO file is not the same as the release on the download servers and is probably corrupt.
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