tominecon.7z is an archive found on the assets.minecraft.net server. The file was uploaded on 2011/11/15 @ 10:23AM. It was later replaced with a decoy on 2012/08/08 @ 10:56AM.
I personally suspect it contains an unreleased demo of the Minecraft Xbox 360 Edition from the original Minecon 2011 showcase. The archive may additionally contain source code and potentially proprietary developer tools for the Xbox 360.
Through online forums around the time the file was first discovered, we've found that the code to the archive is most likely a 16-digit password consisting of only numbers (0-9). For an in-depth explanation on what tominecon.7z is and everything known about it, I highly suggest watching this video by RetroGamingNow.
To use tominecon.7z cracker, open a terminal in the directory of the executable and type ./tominecon_cracker.exe <PATH_TO_TOMINECON.7Z> [NUMBER_OF_THREADS]
The way this works is incredibly inefficient. I made this in the span of like 10 minutes so if anyone has any suggestions to make it faster or thinks the code to the archive may actually be something else, feel free to share.