How can I get different SHA checksums for 'identical' iso files?

0

I have two ISO files, I call it 

Windows 10 ISO #1.iso
Windows 10 ISO #2.iso

The checksums calculated with different tools show two different values for this two *.iso files.
The two textfiles show the different checksums for #1 and #2 (calculated with Nirsofts HashMyFiles.exe)
The two dialog boxes from 7-Zip confirm the different checksums for #1 and #2: enter image description here

How can it be that a tool like KDiff3 doesn't find any difference in the included files and directories and shows everything in "green" as identical? enter image description here

How can it be that the checksums for the two *.ISO files #1 and #2 mounted with Windows 10 file explorer show the IDENTICAL SHA values? enter image description here

In this case: Would you say the ISO are identical or not?

PeterCo

Posted 2019-03-25T14:50:39.673

Reputation: 152

1If check sums are not equal then by definition the files are guaranteed to not be the same. If check sums are equal then there is a high chance that the files are the same, but not 100% guarantee. Now for if the files are "close enough" to function, that is an entirely different question – Eric F – 2019-03-25T14:53:05.220

1Windows Explorer only shows file contents of the image. It does not show boot “sectors” or anything the like. – Daniel B – 2019-03-25T14:59:14.733

"Would you say the ISO are identical or not?" - You should be comparing the hash provided by Microsoft generated by the same tool Microsoft used to calculate the hash they provided. It is not possible to make a determination using the information you provided.

– Ramhound – 2019-03-25T15:03:04.240

1Also, according to MSDN, 2F8910CE2CFAF61F094DFD49FE87AC004A6200AF is the “real” file. – Daniel B – 2019-03-25T15:04:32.633

@DanielB - It is my understanding that Microsoft stopped publishing the checksums for Windows 10 ISOs.

– Ramhound – 2019-03-25T15:09:50.363

1They are not publicly available, that’s correct. However, because I have an active MSDN subscription, I can still view them. – Daniel B – 2019-03-25T15:10:29.583

Answers

2

How can it be that a tool like KDiff3 doesn't find any difference in the included files and directories and shows everything in "green" as identical?

The application is only looking at the contents of the image. You are not comparing the boot sector of the image.

Would you say the ISO are identical or not?

It is not possible to make this determination. You should be comparing the checksum calculated by certutil and compare it to the checksum provided by Microsoft. If you used the Media Creation Tool to download the ISO you are comparing, the checksum will be different, this is intentional behavior by Microsoft.

Ramhound

Posted 2019-03-25T14:50:39.673

Reputation: 28 517

Asked: 2019-03-25T14:50:39.673

Viewed: 139 times

Active: 2019-03-25T15:16:59.683