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Backstory: Recently downloaded an Android ROM, tried to flash it, only to find out it was a corrupted archive. No wonder it didn't work.

I'd like to avoid bigger issues, like an OS ISO corrupted archive would be a far bigger problem than an Android ROM. Are there any download managers for paranoid people? What I mean is actually a download manager where you can insert checksums for downloads (preferably MD5 as I think it's the most common CMIIW), and if they don't match, the manager will 'split' the file if the server supports resume, and download the corrupted piece (I know this sounds magical). Smaller size downloads under 100 MBs hasn't caused me grief. Client sided (like Steam) is also clean.

So far I haven't seen a download manager that supports checksums. As for common issues, I'm pretty sure my RAM and HD are working just fine, I'm constantly playing games without any issues. I know my internet is the issue, but there's no way I can change that ATM.

If possible I'd prefer a Windows program, otherwise an Ubuntu program.

Requirements:

  • inserting checksums
  • comparing sums

Bonus:

  • preferably free
  • 'intelligent' corrupted piece management

Answered: it seems there is no magical download manager yet

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    What I don't understand: How can the download manager know which piece of the "split" file is corrupted without getting an MD5 sum for each piece from the server? Is this something that is implemented in the HTTP protocol and that HTTP servers support? I actually don't know.
    – smheidrich
    Aug 2, 2016 at 21:01
  • @pmos: no, that's techncally not possible. One could certainly invent such a checksum, but it would end up in a concatenated sequence of checksums.
    – Thomas Weller
    Aug 2, 2016 at 21:09
  • @ThomasWeller I looked it up and if the comments on this answer are to be believed, then it is in fact part of the HTTP protocol already, but server developers have unilaterally decided that there is only one MD5 sum and it's always for the whole file.
    – smheidrich
    Aug 2, 2016 at 21:26
  • @pmos: yes. And you would not find that MD5 on a web page, since it's in the HTTP header. Also, it would require HTTP - files are often provided per FTP.
    – Thomas Weller
    Aug 2, 2016 at 21:32
  • thats why i said magical. i doubt something like this existed, yet. if im not mistaken torrents handle things that way, splitting files then comparing to others. i did stumble upon a site recently that allowed us to view checksums before downloading
    – FONZ
    Aug 2, 2016 at 21:52

1 Answer 1

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Free Download Manager can check such values. It supports MD5, SHA-1, SHA-2 and CRC32. After the file was downloaded, select it and press Shift+I or right click it and go to Advanced / Check File Integrity.

  • it works on Windows
  • it is free
  • you can insert a checksum
  • it will compare the checksum against the checksum of the file
  • it has intelligent piece management for the download and will download in multiple connections

Regarding the partial re-download in case of a corruption, that's technically not possible with a single checksum. You would need a checksum for each downloadable part and I've not seen websites providing e.g. a checksum for the first 20 MB, second 20 MB etc.

FDM checking file integrity

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  • gave the older portable version a go on both my computer (home network) and laptop (neighbor). the integrity checker does work when mismatched. im hoping they add that magical component i need since this is probably the most complete download manager (im currently using XDM)
    – FONZ
    Aug 3, 2016 at 7:46

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