md5 check

[bitmapbrother]

Hi, I transferred 8 GB ISO from my friend using ftp. He divided it to 34 parts (split size 200 000 000 bytes) using WinRAR. He also created md5 for each file. I extracted it without problems so I didnt checked md5 and he deleted archives. Later I noticed that two parts of archive have different size (200 310 784 bytes). So I started md5 checks and those two files has wrong md5 check. He also sent me md5 for whole big ISO so I checked it against my ISO extracted from archive and it is correct!?

1) So, now I dont understand how is it possible that md5 of final file match although two parts of archive has wrong md5 check? Is md5 limited up to files of certain size? Is my ISO ok or corrupted?
2) We wanted to create archive again so I can download those two parts but he forget last winrar configuration - is there way to read from RAR archive which options and compression were used?

Thx for your time.

 

[eyec]

to my knowledge MD5 does not have any limitations on files size.

if the ISO checked ok then i would say it is not corrupt.

as for the RAR question i don't know.

did your friend send you the MD5 of the file uncomprossed or compressed and did you run MD5 on the compressed or uncompressed file. just checking.

 

[bitmapbrother]

He send me md5 for each archive part created by WinRAR and md5 for uncompressed ISO file too. Two archive parts have wrong md5 but WinRAR is able to extract ISO out and that ISO has correct md5.

 

[Freestone]

Perhaps he sent you incorrect MD5s for the two files in question. Otherwise, I am with you, your final ISO should have an incorrect MD5.

 

[bitmapbrother]

I found that WinRAR has this option:

"Put recovery record" - "Adds the recovery record, which may help to restore an archive in case of damage. You may specify a size of the recovery record in the Advanced options of this dialog. The default value is about a percent of the total archive size."

Is this option reason why WinRAR extracted ISO correctly even when two parts have wrong md5? It looks like that to me.

 

[eyec]

any change to a file will create a different MD5 value. so, yes that could be the reason for the different values.