End-User-Effort just doesn't work, sadly. I'm currently rather thinking about some cross-referencing service. A developer would go ahead and register multiple

End-User-Effort just doesn't work, sadly. I'm currently rather thinking about some cross-referencing service. A developer would go ahead and register multiple download locations for their product. The system would go ahead and download the file from the various locations, compute checksums and alert if the checksums of different download locations differ. If this service exists, you'd have to compromise this service and a download location in order to exchange a file unnoticed for more than 2*the check interval. The major issues I see: - Updates are a big issue, because updates are a planned exchange of the binary to download. So I guess there'd need to be a set of valid checksums, which weakens the guarantees of the system, but not too much. - Resources are an issue, especially bandwidth and traffic. Imagine getting all debian isos from all mirrors to verify their checksums. But either way, such a service could be a good way to detect irregular file changes and notify the security community, devs, site admins and so on.