French pair compute more than two million combinations to crack code.
Two French hackers have used their skills with computers and logic to reconstruct a blurred QR code on TV and claim bitcoins worth $1,000.
When French channel, France 2 broadcast an interview with entrepreneur Roger Ver earlier this month, he promised he would hand over three Bitcoin Cash coins, worth $1,000 to whatever viewer was the quickest to scan an on-screen QR code he held up with his hands.
All users had to simply do was watch the broadcast and scan the QR code. However, due to French laws, the code was blurred out by the channel, and to all intent and purpose unscannable.
But for two viewers in particular, rather than give up, went to work instead. Michel Sassano and Clement Stork successfully put the QR code together and pocketed the cryptocurrency.
Not that reconstructing the blurred out QR code from was an easy task. The duo noticed that one small part of the code was visible. The keen-eyed pair also noticed that the top of the QR code and part of the key written in letters and numbers were also not totally blocked out.
With that small amount of information the pair were able to reconstruct enough of the QR code that that they could start trying to guess the correct access code to the Bitcoin Cash. The duo later blogged about their exploits.
Let’s be clear, the chances of finding the private key by only brute forcing were close to zero. We knew the property of QR codes and their resilience to damages. Our goal was to gather as many information as possible to make unknown parameters as small as possible. We knew we would have to brute force at some point. After all the steps below, we only had to brute force 2,097,152 combinations.
Easy when you know how
Now, 2.1 million may still seem like a huge number, but thanks to their computers, the two hackers eventually managed to get down “to two valid keys that would match bitcoin private keys,” said Mr Sassano.
From start to finish, the process took some 16 hours, according to their later blog post. The two Frenchmen transferred the cryptocurrency into their own bitcoin wallet on October 17. “The money is the cherry on the cake but the most exciting was when we found the private key and the algorithm told us this was the one,” said Mr Sassano, adding that he had not yet withdrawn the money.
For his part, Roger Ver described the pair’s work as amazing….”With almost no information at all they were able to reconstruct the private key and claim the funds,” he continued. “If you have time to read the blog it’s absolutely incredible.”
And that’s not a bad idea. You can read the full blog post here.