Honestly, I searched through my old hard drive but couldn’t find anything useful. So, I decided to use some data recovery tools, and fortunately, one of them managed to recover a .gpg file—although it was restored with a random name. The file is 165 MB in size and has a .gpg extension.
I ran a full strings scan on it, and it was filled with keywords like “btc”, “wallet”, “xprv”, “priv”, and “key”. I also noticed the beginnings of old Bitcoin addresses. However, all the matches were small fragments—no complete sentences or full addresses.
Then I used the gpg --list-packets command to analyze the file structure. It showed that the file is encrypted using RSA (Key ID starting with 5EB…), with algorithm 3 and an encrypted data packet of length 6284 bytes.
I don't suppose you can go anywhere from this point. The point of encrypting something with RSA (using GPG as a tool), is to
not be able to open it without the password.
RSA encryption is asymmetric. Which means that in order to decrypt the file you will need the private key.
The private key lives inside the hosting machine, where GPG was installed (most of the time).
If (I repeat if), the disc that you have in your hands was the same disc where the OS was installed, or if by chance you have saved the keys in the same disc, there may be a chance to find it.
I would search for
.gnupg in the old disc. If there is any key material there, you may find it this way. But there is a catch. You will need to know the password, which is a very difficult task to accomplish 15 years later.