I don't know, man. They might just be using a device that unlocks with a 4 digit password and they keep it safely inside a locker that opens with hundreds of thumb impressions or thousands of retina scans.
But, corporations also have heads/owners, I'm sure only they have the code.
The proof lies in the fact that Musky's Tesla stopped accepting (now even talking) Bitcoin, for they tried it to do corporate thing with Bitcoin bit it didn't make sense. So, now they only show balnce sheet with Bitcoin and the key is there in Musky's mind. TBH, he is no kid.