I decided to write this guide for anyone who, like myself, wants to convert the mini-private key from stored on the physical casascius coin, into the regular WIF format which can be imported into the Bitcoin Core client, and in the process, to avoid using an external service, such as Gemini.
The reason for not using a service was because I wanted to maintain control of my private keys, just in case. Seems reasonable enough?
In order to convert, I ended up writing a small Java function, which takes the mini-private key format as an input, and outputs the wif string as output. You can pull the project from github via the following link:
https://github.com/unk1911/BitcoinUtilities
If you wish you can include this project in your project as a dependency.
To invoke the conversion function, simply call: Casascius.miniToWif(miniPrivKey)
Once you get the private key, importing it into Bitcoin Core becomes trivial: simply open the debug console window and import using the 'importprivkey' command:
importprivkey "myPrivKey" "fromCasascius"
This will trigger the client to rescan, which could take 1-2 hours, and once completed, your coin will appear in the wallet.
Use the same coin for BTC, as well as the BCH and BTG forks.
For each fork/version, you need to create a separate wallet, preferably running in a different VM, you should plan on allocating at least 250GB of disk to each VM, and preferably use SSD to speed things up, it will take many hours to complete the full procedure.
