First proof of concept: Hiding Bitcoin in plain sight

Hiding Bitcoin is an idea that was discussed in an earlier thread today, and a couple of interesting ideas came up for the realization. Of course, hiding Bitcoin in plain sight can have numerous other uses other than OP's gift card with secret meaning.

I'd like to start exploring these possibilities, starting with QR-codes.

For my first proposal, I've selected a fairly large, highly detailed photo of Copenhagen. I've calculated the local entropy with the Python module scikit-images. Regions with high entropy seem "busy" on their own. In nine manually selected high-entropy regions, I've placed a QR code to a private key.

Here's the image: Bitcoins in Copenhagen (6800x2414 PNG, 28MB)

To make each code less obvious, I've replaced black and white with local colors (for example, dark and bright green when hiding the code in the trees), and reduced the opacity to about 60%. I made sure that in 100% or higher magnification, each code is properly scannable from screen.

This idea is intented to be printed to a real-world poster, for applications where private secrets (e.g., passwords or keyphrases) wouldn't work. To scan the codes, you'd probably need to use a magnifying glass.

And here is the solution to the code locations: solution (800kB)

Of course, you could create a multi-sig wallet instead of redundant keys, but once the obscurity is broken, there's not much point to that.

Please discuss, for example:

• How to print the image so that the codes can still be scanned?

• Which use cases require obscurity, instead of relying on security?

• Which image type is best as a base for this strategy? Open meadows, busy forest floors or chaotic junkyards?