- Bitcoin can’t be hacked by quantum computers because they’re a million times too small.
- Bitcoin is secured by a cryptographic algorithm, making it theoretically vulnerable to cracking by a quantum computer – but in practice, such devices are currently a million times too small to pose a threat.
Bitcoin is theoretically vulnerable to cracking by quantum computers, but calculations show that they would need to be a million times more powerful than those currently in use.
To break the algorithm that secures bitcoin, quantum computers would need to grow about a million times larger than they are now, putting the cryptocurrency at risk from hackers.
The bitcoin network is kept secure by computers known as miners, which use the SHA-256 cryptographic algorithm developed by the US National Security Agency. Breaking this code is essentially impossible for ordinary computers, but quantum computers, which can use quantum physics properties to accelerate some calculations, could theoretically crack it.
Now, Mark Webber and colleagues at the University of Sussex in the United Kingdom have investigated how large a quantum computer would be required to break bitcoin in terms of the number of qubits, or quantum bits, which are the equivalent of ordinary computing bits.
Before a bitcoin transaction can be added to the blockchain, the immutable ledger of who owns what must be “confirmed” by the network of miners. During the confirmation process, each transaction is assigned a cryptographic key, and cracking the key grants you ownership of those bitcoins.
Although bitcoin is secure for the time being, there are concerns about other encrypted data that have a much larger window of vulnerability. Once a quantum computer is available, an encrypted email sent today can be harvested, stored, and decrypted in the future – a so-called “harvest now, decrypt later” attack, which some security experts believe is already taking place.
This is reassuring news for bitcoin owners because current machines have only a tiny fraction of this – IBM’s record-breaking superconducting quantum computer has only 127 qubits, so devices would need to become a million times larger to threaten the cryptocurrency, which Webber believes will take a decade.