Can one detect corrupted ISO?

[Squall]

I have seen many bug reports in which the problem is in the corrupted ISO.
An example: https://github.com/hrydgard/ppsspp/issues/3034

I wonder if algorithms like MD5 or SHA can detect corrupted ISO by checking uncompressed files. CSO files would have to be uncompressed by an intermediate way.

The question is: If no error happens, will the ISO files produced with any UMD of the game on any PSP always be exactly the same?

[solarmystic]

(08-05-2013 12:12 AM)Squall Wrote:  I have seen many bug reports in which the problem is in the corrupted ISO.
An example: https://github.com/hrydgard/ppsspp/issues/3034

I wonder if algorithms like MD5 or SHA can detect corrupted ISO by checking uncompressed files. CSO files would have to be uncompressed by an intermediate way.

The question is: If no error happens, will the ISO files produced with any UMD of the game on any PSP always be exactly the same?

You don't even need to decompress the files from the ISO. Just run a MD5 or SHA-1 check on the ISO itself.

A reference library of correct SHA-1 or MD5 values for each title in a certain region could be theoretically constructed and used as a reference to indicate whether or not the ISO is corrupted.

They should all match one another with the following caveats:-

1. They're from the same region, with the same region id.

2. They were dumped correctly (truncated dumps don't count)

3. They're at the same patch/update level.

4. They're also not "fixed" (fixing in this instance means modified to use with Prometheus and other loaders) or cleaned and are pristine.

The precise size (down to the byte level) could also be used, but it is way more inaccurate to determine these things.

[Squall]

I think we can use the no-intro dat as reference:
http://datomatic.no-intro.org/?page=download

And Quick Hash GUI to get SHA-1 and MD5:
http://sourceforge.net/projects/quickhash/