Is it possible to get corrupted download with http?

Solution 1:

Yes, it's possible, especially on poor quality Internet connections – usually wireless, but some wired connections ^{(such as the one I have)} also have high error rates at high speeds.

The HTTP protocol does not have any provisions for ensuring data integrity. On transport layer, TCP does have error detection by using a checksum, but it's not very reliable.

There is another reason for providing hashes or digital signatures. Often, the actual files are distributed over many mirror servers, which cannot be guaranteed to be 100% secure. If there's no hash or signature to verify, someone with access to a mirror (not necessarily legitimate) could replace the files and remain undetected, without having to break into a completely different server where the website is hosted.

You can get automatic verification of files if you download Ubuntu over BitTorrent instead of HTTP. (Each piece is verified at download time, so you never have to re-download the entire thing.)

Solution 2:

As Grawity said, it is possible, but in addition, what I have noticed:

Even with stable internet connections, it is possible for a download to finish early without any sort of valid reason - it can just happen.

And most importantly, if you have bad memory, it is possible that the download caches in memory before being written to disk, and as the memory is bad, it is writing the file incorrectly. If you constantly have bad downloads, this is a high posibility.