What? If someone cryptographically timestamped a particular signed file in 2005, even if Eve cracks the original public key and can now produce arbitrary new signed files with that key, they still do not have 2005 timestamps for any of those new files! They could only make 2015 timestamps. That's the whole point of cryptographic timestamps.
(If you could certify a timestamp forever, in a non-expiring, uncrackable way, why wouldn't you just use that for the whole file?)
OK, so you don't actually understand how cryptographic timestamping works or the Bitcoin version. Please read up on it before commenting.
> If you could certify a timestamp forever, in a non-expiring, uncrackable way, why wouldn't you just use that for the whole file?
What you are timestamping is the whole file!
(Of course the time stamp is for the whole file; not just for a subrange of bytes or whatever; if anything is altered, then the timestamp doesn't hold for the altered object.)