<p>To 'own some bitcoins' is to own the private key that allows a UTXO to be spent, so your question can be refined to "<em>how do you verify ownership of a private key that controls a UTXO?"</em></p>

<p>There are a few ways you could do this:</p>

<ul>
<li>Sign a generic message with the key, such as <em>"I am the owner of bitcoin address 1a5Ag23...."</em></li>
<li>Sign a transaction with the key, spending the coins to a new address (you could post the address prior to broadcasting the tx, to prove the coins are not just moving by coincidence)</li>
<li>You could show off the private key itself (but this is a very bad idea! The bitcoins probably would not remain yours for long...)</li>
</ul>

CC BY-SA 3.0
2018-03-23T00:09:42.700Z
I disagree that owning BTC is equal to having access to private keys. Coinbase certainly does not own all the BTC they have keys for, for example.
Pieter Wuille
CC BY-SA 3.0
2018-03-23T00:24:27.743Z
@PieterWuille I guess it is helpful to differentiate between 'ownership according to the blockchain' and 'ownership according to legal/social contracts'. In any case, the UTXOs  Coinbase controls would not map perfectly onto user account balances, so we can't really point to a specific CoinBase-controlled UTXO and say *"that one belongs to user x"*. Coinbase may be reputable and have intent to fulfill their duties as a custodial service, but sketchy exchanges that have exit scammed in the past help prove my point. If someone owes you $5 but hasn't paid it back, you don't own that $5. They do.
chytrik
CC BY-SA 3.0
2018-03-23T00:25:22.277Z
In this sense, perhaps it would be better to say 'Control of the UTXO', rather than 'Ownership of the UTXO'. I think that satisfies both of our arguments.
chytrik
CC BY-SA 3.0
2018-03-23T00:36:34.593Z
I think there's a difference between money owed (a debt) and custodial control. Even the sketchiest exchange doesn't own your money - you're perhaps making a bad business decision to risk having them control it, but it in no way makes the money owned by them. I think ownership is inherently a social construct, and not something described by the blockchain. The latter is just a way to reduce risk of having the wrong parties take control. It's even more complicated with UTXOs controlled by escrow or hashlocked contracts. These don't have a clear identifiable owner key even.
Pieter Wuille
CC BY-SA 3.0
2018-03-23T03:33:38.567Z
Nonetheless, the answer does not delve into ownership of BTC. Coinbase certainly has ownership of the private keys needed to sign for each utxo.
Willtech
CC BY-SA 3.0
2018-03-23T00:02:36.897Z
2018-03-23T00:02:36.897Z
chytrik
<p>Is there any other way besides signing a transaction to verify ownership of utxos?</p>

<transactions><validation>
Verifying ownership of utxos
Errol
# Verifying ownership of utxos

(Asked by: username_0 on 2018-03-22)

Is there any other way besides signing a transaction to verify ownership of utxos?

**Tags:** transactions, validation


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## 1 answers

### Answer by username_1 on 2018-03-23. Score: 3

To 'own some bitcoins' is to own the private key that allows a UTXO to be spent, so your question can be refined to "*how do you verify ownership of a private key that controls a UTXO?"*

There are a few ways you could do this:

* Sign a generic message with the key, such as *"I am the owner of bitcoin address 1a5Ag23...."*
* Sign a transaction with the key, spending the coins to a new address (you could post the address prior to broadcasting the tx, to prove the coins are not just moving by coincidence)
* You could show off the private key itself (but this is a very bad idea! The bitcoins probably would not remain yours for long...)

> **Comments:**
> **username_2**: I disagree that owning BTC is equal to having access to private keys. Coinbase certainly does not own all the BTC they have keys for, for example.  
> **username_1**: @PieterWuille I guess it is helpful to differentiate between 'ownership according to the blockchain' and 'ownership according to legal/social contracts'. In any case, the UTXOs  Coinbase controls would not map perfectly onto user account balances, so we can't really point to a specific CoinBase-controlled UTXO and say *"that one belongs to user x"*. Coinbase may be reputable and have intent to fulfill their duties as a custodial service, but sketchy exchanges that have exit scammed in the past help prove my point. If someone owes you $5 but hasn't paid it back, you don't own that $5. They do.  
> **username_1**: In this sense, perhaps it would be better to say 'Control of the UTXO', rather than 'Ownership of the UTXO'. I think that satisfies both of our arguments.  
> **username_2**: I think there's a difference between money owed (a debt) and custodial control. Even the sketchiest exchange doesn't own your money - you're perhaps making a bad business decision to risk having them control it, but it in no way makes the money owned by them. I think ownership is inherently a social construct, and not something described by the blockchain. The latter is just a way to reduce risk of having the wrong parties take control. It's even more complicated with UTXOs controlled by escrow or hashlocked contracts. These don't have a clear identifiable owner key even.  
> **username_3**: Nonetheless, the answer does not delve into ownership of BTC. Coinbase certainly has ownership of the private keys needed to sign for each utxo.  

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