<p>The simple explanation is that the attacks that quantum computing enables require information (the public key) that isn't available until after the first transaction is seen.  </p>

<p>Until the first transaction spending an output, all that is known is the hashed version of the recipient key (aka the address) which isn't enough to mount the attack.  If fully developed quantum computers appear with no warning and somehow make it into the hands of a large miner they could potentially see an incoming transaction and race the transaction but the odds of this are vanishingly small.  Most likely, as QC becomes more of a danger, the algorithms in bitcoin will be swapped out for QC resistant ones.</p>

CC BY-SA 3.0
2016-05-14T05:05:01.377Z
2016-05-14T05:05:01.377Z
Jonathan
<p>Though quantum computing can technically break ECDSA with enough qubits, this has not the greatest implication on btc because public keys are not known as they are protected by the hashing used to create an address.</p>

<p>However, I've noticed online it's been said a few times that reusing addresses may reveal your public key?</p>

<p>Is this true?  Are there times your public key is revealed and quantum computers become a legitimate threat?</p>

<public-key><quantum-computing><address-reuse>
Does address-reuse make Bitcoin private keys vulnerable to quantum computing?
tacoma
# Does address-reuse make Bitcoin private keys vulnerable to quantum computing?

(Asked by: username_0 on 2016-05-14)

Though quantum computing can technically break ECDSA with enough qubits, this has not the greatest implication on btc because public keys are not known as they are protected by the hashing used to create an address.

However, I've noticed online it's been said a few times that reusing addresses may reveal your public key?

Is this true? Are there times your public key is revealed and quantum computers become a legitimate threat?

**Tags:** public-key, quantum-computing, address-reuse


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## 1 answers

### Answer by username_1 on 2016-05-14. Score: 3 | Accepted answer

The simple explanation is that the attacks that quantum computing enables require information (the public key) that isn't available until after the first transaction is seen.

Until the first transaction spending an output, all that is known is the hashed version of the recipient key (aka the address) which isn't enough to mount the attack. If fully developed quantum computers appear with no warning and somehow make it into the hands of a large miner they could potentially see an incoming transaction and race the transaction but the odds of this are vanishingly small. Most likely, as QC becomes more of a danger, the algorithms in bitcoin will be swapped out for QC resistant ones.


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