<blockquote>
<p><strong>How does public address “know” private key?</strong></p>
</blockquote>
<p>It doesn't. There's no need.</p>
<p>When <strong>receiving</strong> money, nobody needs to know anything from you other than your receiving address (in reality a Bitcoin script, the most common types of which can be displayed as an address). At this point no-one cares about <em>your</em> private key.</p>
<hr />
<blockquote>
<p><strong>If later wanting to sell the Bitcoin,</strong></p>
</blockquote>
<p>When <strong>spending</strong> money, you have to provide proof that you know the private key corresponding to that receiving address, without revealing the private key. This is what your wallet does when constructing the transaction details that are sent out for miners to pick up.</p>
<p>Other Bitcoin nodes (wallets, miners etc) can mathematically check that the proof matches the public key and will then know that you have the secret number known as a private-key.</p>
<hr />
<p>See</p>
<ul>
<li><a href="https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm" rel="nofollow noreferrer">https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm</a></li>
</ul>

CC BY-SA 4.0
2021-02-25T23:48:13.753Z
<<<When spending money, you have to provide proof that you know the private key corresponding to that receiving address, without revealing the private key.<<<   Thanks, so only proof is provided that you know the private key when selling, but not the actual private key. Interesting.
SammyJunior
CC BY-SA 4.0
2021-02-24T10:01:14.890Z
2021-02-24T14:26:06.880Z
2021-02-24T14:26:06.880Z
RedGrittyBrick
<p>Imagine the following:
someone goes to the .org address of bitaddress, then <strong>switches off internet connection</strong>, then moves the mouse around until eventually the JavaScript Client-Side Bitcoin Wallet Generator produces a Bitcoin address with its corresponding Bitcoin private key, then saves everything on the screen to <strong>cold storage</strong> as a PDF, then scans the &quot;Share&quot; QR code onto a phone, then scans this QR code at a Bitcoin ATM to purchase Bitcoin and the Bitcoin in deposited in the wallet and this is confirmed on blockchain.
If later wanting to sell the Bitcoin, how does this public Bitcoin address &quot;know&quot; what the correct private key is?
That is, if the Bitcoin public address and private key have only existed on a non-internet connected PC and as a PDF in cold storage?</p>

CC BY-SA 4.0
2021-02-24T08:46:39.707Z
Does this answer your question? https://bitcoin.stackexchange.com/questions/102930/where-does-it-go-and-who-verifies-private-keys
Pieter Wuille
<wallet><storage>
How does public address "know" private key?
SammyJunior
# How does public address "know" private key?

(Asked by: username_0 on 2021-02-24)

Imagine the following:
someone goes to the .org address of bitaddress, then **switches off internet connection**, then moves the mouse around until eventually the JavaScript Client-Side Bitcoin Wallet Generator produces a Bitcoin address with its corresponding Bitcoin private key, then saves everything on the screen to **cold storage** as a PDF, then scans the "Share" QR code onto a phone, then scans this QR code at a Bitcoin ATM to purchase Bitcoin and the Bitcoin in deposited in the wallet and this is confirmed on blockchain.
If later wanting to sell the Bitcoin, how does this public Bitcoin address "know" what the correct private key is?
That is, if the Bitcoin public address and private key have only existed on a non-internet connected PC and as a PDF in cold storage?

**Tags:** wallet, storage

> **Comments:**
> **username_1**: Does this answer your question? https://bitcoin.stackexchange.com/questions/102930/where-does-it-go-and-who-verifies-private-keys  

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## 1 answers

### Answer by username_2 on 2021-02-24. Score: 1

> **How does public address “know” private key?**

It doesn't. There's no need.

When **receiving** money, nobody needs to know anything from you other than your receiving address (in reality a Bitcoin script, the most common types of which can be displayed as an address). At this point no-one cares about *your* private key.

---

> **If later wanting to sell the Bitcoin,**

When **spending** money, you have to provide proof that you know the private key corresponding to that receiving address, without revealing the private key. This is what your wallet does when constructing the transaction details that are sent out for miners to pick up.

Other Bitcoin nodes (wallets, miners etc) can mathematically check that the proof matches the public key and will then know that you have the secret number known as a private-key.

---

See

* <https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm>

> **Comments:**
> **username_0**: <<<When spending money, you have to provide proof that you know the private key corresponding to that receiving address, without revealing the private key.<<<   Thanks, so only proof is provided that you know the private key when selling, but not the actual private key. Interesting.  

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