How can you check if any of your public keys have been exposed?

[headingnorth]

The two main things to follow for best practices handling bitcoin transactions:

1. Don't re-use addresses
2. Don't spend from the same UTXO or address more than once

So is there a way to check if any of your public addresses have been exposed
(ie: in your Sparrow wallet, or other way to do it?)

In other words, you may not recall the details of every transaction you have ever made
(ie: if you have spent more than once from the same address, or re-used an address)
so is there a way to check for that in the transaction history?








Title Correction: public addresses keys

[hosemary]

So is there a way to check if any of your public addresses have been exposed

I am not sure I am understanding you correctly.
All bitcoin transactions are recorded in the blockchain and are visible to the public. So, once you receive a transaction, anyone in the world can see your address and your transaction.

so is there a way to check for that in the transaction history?

You can easily use any block explorer to see whether an address has been reused or not.

[headingnorth]

So is there a way to check if any of your public addresses have been exposed

I am not sure I am understanding you correctly.
All bitcoin transactions are recorded in the blockchain and are visible to the public. So, once you receive a transaction, anyone in the world can see your address and your transaction.

If that is true then what good does it do to not re-use addresses? This is confusing.
Everyone says you can protect your bitcoin from quantum hacking by not revealing your public address.
To do that, don't re-use addresses and don't spend from the same address more than once.

That is what they tell you to do on the Trezor website, and many other credible sources.
So what is the point of taking all these security measures if everything you do is exposed anyway?

so is there a way to check for that in the transaction history?

You can easily use any block explorer to see whether an address has been reused or not.

I have no idea how to do that.

[LoyceV]

Everyone says you can protect your bitcoin from quantum hacking by not revealing your public address.

"Everyone" says that's your public key, not your address.
Here's a legacy address holding 55,078.81978073 BTC with exposed public key. As long as they don't worry about quantum computing, I don't worry about it.

[hosemary]

If that is true then what good does it do to not re-use addresses? This is confusing.

When you reuse an address, people can link your transactions with each other and that's why it may violate your privacy.
Assume that I want to sell something to you and give you my bitcoin address. If I use that address in the future for other transactions, you can know that those transactions are mine.

Everyone says you can protect your bitcoin from quantum hacking by not revealing your public address.

You are confusing address with public key.
Your address is revealed once you receive a bitcoin transaction and your public key is revealed once you make a transaction.

I have no idea how to do that.

There are many block explorers that can be used for checking bitcoin transactions.
You can paste any of your bitcoin addresses in mempool.space or blockchair.com to see all bitcoin transaction associated with that.

[headingnorth]

If that is true then what good does it do to not re-use addresses? This is confusing.

When you reuse an address, people can link your transactions with each other and that's why it may violate your privacy.
Assume that I want to sell something to you and give you my bitcoin address. If I use that address in the future for other transactions, you can know that those transactions are mine.

Yes, that is my understanding.

Everyone says you can protect your bitcoin from quantum hacking by not revealing your public address.

You are confusing address with public key.
Your address is revealed once you receive a bitcoin transaction and your public key is revealed once you make a transaction.

Yeah I got them mixed up.

So what if you send say $100 of bitcoin to yourself, then later spend $20 from that same UTXO
(also to yourself) within the same wallet. Is your public key exposed?

(A couple of years ago I created a couple of hidden wallets for security purposes. So I was sending a bunch of
UTXOs from my main (parent) wallet to the new hidden wallets. In case you're wondering the reason for all
the self sending transactions.)

I have no idea how to do that.

There are many block explorers that can be used for checking bitcoin transactions.
You can paste any of your bitcoin addresses in mempool.space or blockchair.com to see all bitcoin transaction associated with that.

I know I can use block explorer, but I don't know how. I was just wondering if there was a simpler
way to do it without having to learn the block explorer.

[hosemary]

So what if you send say $100 of bitcoin to yourself, then later spend $20 from that same UTXO
(also to yourself) within the same wallet. Is your public key exposed?

Yes.

I know I can use block explorer, I don't know how. I was just wondering if there was a simpler
way to do it without having to learn to use block explorer.

It's really simple to use block explorers to check bitcoin transactions. All you need to do is to paste your address or transaction ID.

Your wallet should also display your transaction history and you can also create a watch-only wallet with your addresses or your master public key, if you don't want to have your private keys on an online device due to security reasons.

[headingnorth]

So what if you send say $100 of bitcoin to yourself, then later spend $20 from that same UTXO
(also to yourself) within the same wallet. Is your public key exposed?

Yes.

Is there any way to guard your coins against potential quantum threats after the public key is exposed?

Other than using Coinjoin?

[LoyceV]

Is there any way to guard your coins against potential quantum threats after the public key is exposed?

Move them to a new address.

[headingnorth]

Is there any way to guard your coins against potential quantum threats after the public key is exposed?

Move them to a new address.

So simply move every UTXO in my sparrow wallet to a brand new address or addresses?
Because the new address is only receiving, hasn't been spent from yet? I think I got it.

So the private key public key that was previously exposed is useless to a hacker, since it no longer has any bitcoin?

EDIT: correction

[LoyceV]

So the private key that was previously exposed is useless to a hacker, since it no longer has any bitcoin?

You mean the public key. If your private key is exposed, your funds are stolen instantly. But really, if you're confused about the difference between addresses, public keys and private keys, you shouldn't be worrying about quantum computing at all. There are much bigger risks factors, like the hot wallet you're using.

[headingnorth]

So the private key that was previously exposed is useless to a hacker, since it no longer has any bitcoin?

You mean the public key. If your private key is exposed, your funds are stolen instantly. But really, if you're confused about the difference between addresses, public keys and private keys, you shouldn't be worrying about quantum computing at all. There are much bigger risks factors, like the hot wallet you're using.

Yeah sorry I meant public key. I mistyped.

Sparrow isn't a hot wallet. It requires a physical hardware wallet to sign transactions.
(It's just an interface and management tool).

I have no idea how to do that.

There are many block explorers that can be used for checking bitcoin transactions.
You can paste any of your bitcoin addresses in mempool.space or blockchair.com to see all bitcoin transaction associated with that.

If I knew how to use a block explorer I wouldn't be in the tech support forum asking the question.
They don't exactly come with instructions (but they probably should).


Let me put it very simply for anyone who knows, what does a public key look like? What is an example of one?

[Mia Chloe]

So is there a way to check if any of your public addresses have been exposed
(ie: in your Sparrow wallet, or other way to do it?)
so is there a way to check for that in the transaction history?

To start with nope. Firstly nodes you are connected to can see your full transaction history which is basically same major data your public keys gives. Aside from this, the bitcoin network uses a public ledger so if someone is watching your addresses there no way you can tell except they probably create a watch only wallet with your public keys and create an unsigned transaction ( which is very unlikely).

As for address reuse you don't have to worry much since your wallet automatically shuffles them out to improve privacy the problem could come in when you receive from a particular address over and over again.

Sparrow isn't a hot wallet. It requires a physical hardware wallet to sign transactions.

You are wrong. It can be used as a hot wallet or a cold one depending on if you use internet or not.

[headingnorth]

Sparrow isn't a hot wallet. It requires a physical hardware wallet to sign transactions.

You are wrong. It can be used as a hot wallet or a cold one depending on if you use internet or not.

Been using sparrow for years, never heard of it being used as a hot wallet.
Either way I have never used it as one, but arguing about it is pointless. Doesn't answer
my original question which is very simple (what does a public key look like).

[Mia Chloe]

Been using sparrow for years, never heard of it being used as a hot wallet.
Either way I have never used it as one, but arguing about it is pointless.

Sighs... Sparrow is just an open source wallet. Your use case now depends if it would be classified as a hot wallet or a cold wallet. Consider  having two sparrow wallets one you use to pay readily for transactions and orders and another which you store your coins in. If you have the first constantly connected to the internet to make transactions then it's a hot wallet. For the second it's a cold wallet if you refuse to connect it to the internet because of risks of losing your hodlings.

my original question which is very simple (what does a public key look like).

This wasn't your original question. Anyways public keys have different format as considering if it's compressed or not . Just toggle to your wallet details you'll find it there if that's what you are looking for.

[mcdouglasx]

public keys are usually exposed when you send btc, I say as a general rule, because in most cases it is, however there are transactions that do not expose their public keys of their addresses, currently you should not be worried about any vulnerability related to quantum regarding whether your public key is exposed or not, it is more of a privacy issue than a risk of losing money, since with your public key you would only be in danger if you use software with a bug that makes your private keys insecure or signs your transactions in an insecure way, such as repeating 2 signatures with the same nonce, therefore if you are not worried about the privacy issue, and you use appropriate tools you could keep 1 address in use without problems, although it is a bad practice in terms of privacy, it does not involve a risk in cryptographic security.

[Obim34]

Is there any way to guard your coins against potential quantum threats after the public key is exposed?

Quantum threat requires a lot of computing power to successfully break through, so don't bother about it for now.

Either way I have never used it as one, but arguing about it is pointless.

When you ask questions and ready to learn, you don't argue. When replies are given here try to confirm instead of thinking to argue, every body wants to learn also, heard of BIP 360 which covers the question you asked about quantum threat.

[headingnorth]

Is there any way to guard your coins against potential quantum threats after the public key is exposed?

Quantum threat requires a lot of computing power to successfully break through, so don't bother about it for now.

You don't know that, which is why it is better to be prepared as best as possible. Better to be safe than sorry.
The quantum breakthough could come at any moment. It is impossible to predict when that moment will come.
It could be 10 years from now or it could be in ten days, or it could be never.

Unless you are a psychic no one can predict the future of when or if the quantum threat will be real.

Either way I have never used it as one, but arguing about it is pointless.

When you ask questions and ready to learn, you don't argue. When replies are given here try to confirm instead of thinking to argue, every body wants to learn also, heard of BIP 360 which covers the question you asked about quantum threat.

Then why are you here arguing with me? If you don't have the answer to the
very simple question that I asked then don't waste my time.

[Skjadoon]

So as long as you use secure tools, there’s no real risk losing coins just because your public key is exposed

it’s mainly a privacy concern, not a security one.

[nc50lc]

1. Don't re-use addresses
2. Don't spend from the same UTXO or address more than once
-snip-
Title Correction: public addresses keys

Another correction: #2 should be rephrased because a UTXO can only be spent once while an address (pubKeyhash) can be associated with multiple UTXO.
As its acronym means "Unspent Transaction Output", it's pointing to a specific unspent output of a transaction and not the pubKeyhash itself.

Removing "...UTXO or..." should be good enough because the new meaning could mean: to spend all of the address' UTXO if it's used to receive more than once.
Then to pair that with #1, do not use it again to receive bitcoins after spending.

So is there a way to check if any of your public addresses have been exposed
(ie: in your Sparrow wallet, or other way to do it?)

That depends on the wallet that you're using.
Some only requires you to check the address list, some requires you to check every address' history for "outbound" transactions.

In Sparrow for example, you can go to its 'Addresses' tab and look for addresses that can be expanded (">" button).
That indicates that it has transaction history, from there, check if it has an expandable "Receive from" transaction which mean that there's a "Spent by" transaction that spent it.

The gist is, if it's used to send at least once, its public key is already exposed.