On Dec 27, 8:54pm, Eric Hughes wrote:
I take it you mean recompile the binary every time? Because you'd need to have source around to recompile it from, and the attacker could modify that source even more easily than he or she could hack the binary. The idea is to make tampering with the binary detectable.
Recompile the binary from newly uploaded source each time. MD5 source isn't more than about 10K long. That's all of a few seconds of upload time.
Irritating, and also insecure (system admin intercepts the upload and replaces it with source of his or her own). As has been stated, it's a matter of defining a threat model. IMO, the most likely threat is from pass phrase grabbing (from a sniffer, annex box or whatever), which destroys the security of almost all of these schemes. Modification attacks are possible, although I doubt that the lengths I have described would be useful. As a serious project, though, a personal version of tripwire would not be a bad cypherpunk project, and possibly a nice testbed for working out some anti-tampering techniques.
I am pretty much certain that to make such a system perfectly secure under these conditions is impossible.
That's right.
Is there a standard proof for this, though? I suspect that there is, but have not discovered it. Ian.