I missed that part. I mean people are sending their BTC to them. How are they tying the payment to the computer?
I was questioning myself exactly this. Maybe the ransomware hás a place to input txid?
Hmm... The ransomware would then need to centrally keep track of which transaction ids have been used.
What is somebody just copies the transaction id once the transaction is broadcast and keys it into the ransomware?
Looking at the image in the Twitter link above, perhaps once you send the required amount, it is automatically decrypted. They actually let you decrypt some files at no cost to prove it works. Nice of the crooks to give you a free sample.