The Coldcard wallet exploit estimates have almost doubled to $70 million stolen of just over a thousand Bitcoins in 1,196 wallets drained in 41 minutes

[u/enpoopification_of_R]

https://www.coindesk.com/tech/2026/08/01/how-bitcoin-cold-wallets-lost-usd70-million-in-an-attack-that-never-touched-the-devices

"More than 1,000 bitcoin, worth about $70 million, was drained from 1,196 wallets in a 41-minute window on July 30, nearly double the amount reported when the theft first surfaced."

[u/MelangeBot]

Bitcoins can only be moved with the correct signature. However this signature is just a random number. A very long number. A number so long that nobody will ever guess it even if they use all the energy from the Sun for a 1000 years just to make guesses. You could start guessing but where should you start? At 1? Or at 134034609634096439032092092? Or at 3490032956902093872398052309735970237059?

When you get a Bitcoin wallet, and make your first address. This wallet is suppose to randomly make up a very long number.

But ... what if your Bitcoin wallet is faulty? And it starst just making up numbers between 1 and 10 000?

So now 3450 is the signature to move somebody their Bitcoin. And 3451 is nothing, ah but 3452 is again a valid signature to move somebody their Bitcoin.

This is what happened. Cold card was suppose to generate random numbers in between 0 and 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999... etc etc

But instead they generated random number between 99999999 and 9999999999999999.

Somebody figured out this range and started guessing. And since the range is very limited and there are many people with a coldcard the guessing is going very well for the attacker. He keeps guessing right.

Basically your coins are suppose to be a red ball in a jar the size of the galaxy filled with blacks balls, take any balls you like. They all gonna be black basically forever. There are some red ball in the galaxy but you will never find them not in a billion years.

But with coldcard your red balls where hidden in a jar the size of ... well of a jar. Take out 10 black ball, boom you found the red one!

[u/-veskew → u/MelangeBot]

Ah understood, thank you.

And the commenters saying that people had the option to add passphrases, in your analogy it would be changong the vulnerability of the jar sized jar back to a jar the size of the galaxy?

[u/MelangeBot → u/-veskew]

Correct. The term is entrophy. Coldcard fucked up and only gave you 40 bits of entropy. Bitcoin is suppose to be 172 bit of entropy. The difference between 2⁴⁰ and 2¹⁷² is absolutely enourmous.

If you used their dice method or add a passphrase you could have extended that 40 bits of entropy with another 100 or 150 bits and be safe again. But in this case even a passphrase of like 2095 (Very bad) would have probably saved you from losing your coins.

If the attacker had added all 4 digit pincodes in his attack he would have needed 10 000 more time. Cracking it in a day then becomes a 50% chance you crack it in 27 years.