Quote from: Mike3574 on May 03, 2012, 06:00:00 AM

I appreciate you bringing these things to my attention. I have inside the zip files the hashes of the individual files contained inside. However, as you said, if someone is able to modify that then it doesn't really matter. I will makes hashes of the actual zip files (which are still on my PC) and add them to the page. Would that solve this problem? Or is there still another way around it for an attacker? Please let me know. I want to do all I can to ensure that nothing is tampered with.

No, it won't solve the problem, and the way for the attacker to get around it is... the same way, actually. If someone is modifying the responses from your site, the can modify the page source (as received by the victim) just as easily as the zip files, and they can just replace your hashes with the hashes of the modified files. You need PGP signatures, not hashes, to protect against this attack (though even that won't work unless your PGP key is already available from a trusted source). Or SSL. Or both, if you're really paranoid.

EDIT: I just realised something. I don't know about other cryptocurrencies, but in Bitcoin each block contains a hash of the previous block, and therefore the Bitcoin client will instantly know something's gone horribly wrong when it downloads the next block and the hash doesn't match the blocks it already has, and will fix the problem by re-downloading the "erroneous" blocks. The only way this won't happen is if the maliciously altered blockchain has a higher total difficulty than the real one, in which case they don't even need to attack your site - we're all doomed anyway. Only light clients (which don't need a blockchain download anyway) have a need to implicitly trust the blocks they receive. Exactly how does a maliciously altered blockchain pose any kind of threat?