Security experts revealed a troubling new flaw in Bitcoin hardware wallets known as “Dark Skippy.” This vulnerability allows hackers to steal private keys using only two signed transactions, which is a major improvement over older methods that required many more transactions.
How the Attack Works
The report, published by Lloyd Fournier, Nick Farrow, and Robin Linus, explains how the Dark Skippy attack operates. The attack begins when hackers trick a user into installing harmful firmware on their hardware wallet. This malicious firmware hides parts of the user’s seed words within “low entropy secret nonces” used in transaction signatures.
When these signatures are added to the blockchain, attackers can analyze them to reveal the original seed words. They use Pollard’s Kangaroo Algorithm to transform the public nonces into secret nonces, effectively uncovering the hidden seed words.
Impact and Safety Measures
This flaw impacts all models of hardware wallets but only works if the attacker manages to install the fake firmware on the victim’s device. Unlike older methods that required many transactions, Dark Skippy can be carried out with just two transactions. This makes it much easier for hackers to exploit the flaw.
The attack can still succeed even if the seed words are generated on a separate device. This new method is a significant advance from previous vulnerabilities, which needed many more transactions to be effective.
To reduce the risk, the researchers recommend that hardware wallet manufacturers enhance their security features. They suggest adding secure boot systems and thorough firmware checks to prevent malicious firmware from being installed. Users should also take steps to secure their devices, though some of these measures might be difficult to follow.
In summary, the Dark Skippy flaw poses a serious threat to Bitcoin hardware wallets. It allows hackers to access private keys more easily than older methods. Both manufacturers and users need to strengthen their security practices to protect against this new threat.
