The problem is not that digital information is inherently unsafe, it’s that the people with access to that information are inherently unsafe.
This has, of course, always been true. But 25 (copiers) or 50 (camera) years ago the guy who passed the information to wikileaks would have been able to get only a few documents out at most, not hundreds of thousands of pages.
Digital format merely makes it multiple orders of magnitude easier to copy and send information. Some small percentage of those with access will choose to do so. I know of no way to 100% eliminate the chance of somebody with access making such a choice.
It’s the same as with guns. Guns don’t kil people, people do. But guns make doing so much easier.
ML/NJ
You are 15 years off on copiers (they were reasonably common at the Pentagon c. 1970), and ~25-30 years on cameras.