[Mosteran]

It's not easy to secure it. You have to do two things very well:

1) Don't let anyone find the private key

2) Don't let yourself lose the private key

The more of 2 you do, the harder 1 gets and the more of 1 you do, the harder 2 gets. If you have only a single copy on paper, it's hard for anyone to find, but also easily damaged or lost. If you make a backup on a computer, a virus might find it, making the paper copy worthless.

Not only that, but from the moment you generate the key, you have to be completely confident about the security of the computer you're using. People recommend a clean install of OS from the original CD and never connecting to the internet. That's not impossible but not easy, furthermore you have to carefully destroy all record of it left on that computer. So unlike gold, not only do you have to keep it secure in the future, but you have to have made sure that it was always secure throughout the past. You can't transfer ownership to anyone else without them going through the same rigmarole too, unlike gold which you can physically give to someone and they can be confident it won't evaporate in front of their eyes one day.

I agree with you about blockchain analysis. Who knows what new techniques might be able to dig up. They might not have much certainty but perhaps enough to put suspicion on someone.