Low fees of 1 or 2 satoshis per vByte are an excellent opportunity to
make your coins more safe and private. You can even make them almost quantum-safe - in 2025!
Well, in many cases, you may already have done your homework. But if not, then this post ist a reminder
New bitcoiners often make a mistake: they often
re-use their Bitcoin addresses. Some think that a Bitcoin address is kind of an "identity", or an "account", like some altcoin communities like Ethereum's told them. But that is not the case!
Bitcoin is best used without re-using addresses. [1] There are two main reasons:
1) Re-using Bitcoin addresses make it easier for any entity, for example chain analysis companies, but also thieves and scammers, to link your coins together. In short: Your privacy is at risk! (See also
this post).
2) When you spend coins from an address, you expose your public key for this address and store it to the blockchain. In the future, this may enable
attackers with quantum computers to compute the private key using the public key and steal your coins! [2] [3]
There's an easy fix:
simply move the coins on the re-used addresses to a freshly generated address! Both Bitcoin Core and the popular SPV wallets like Electrum or Sparrow provide easy means to do that.
1) Simply select the tab or menu item where your addresses are shown.
2) Select an address which was not used. In Electrum for example, you see the number of transactions made with this address under the column "Tx". If it is zero, then you can use this address.
3) Copy this address.
4) Now you have two options to spend them:
4a) If you have coin control enabled, then it's best to separate the coins according to the address where you received them. Select all coins which are on the same address, add them to coin control, and then send all these coins to a fresh address.
4b) If you don't have coin control enabled or don't know how to use it, or you have only one or two re-used address(es), then you can simply send all the Bitcoins to the fresh address.
Note:There is a special class of re-used addresses: those where you only received coins, but never spent them. This is typically the case in bounty campaigns when you decide to hodl all rewards.
It is a good idea to eventually move these coins to a fresh address too, but in this case it is best if you then never use this address again. So if you want to continue to hodl the coins which arrive in this address and not spend them, it's not necessary to move them.
Note 2:If you for any reason still have coins which were received with a P2PK script, i.e. paid directly to a public key instead to an address, move them too! This is often the case if you mined in the early years of Bitcoin. They're not less private, but they are vulnerable to quantum computing attacks just like coins on re-used addresses. It's unlikely you're a beginner in this case though
[1] Well, there are some cases where re-using addresses is convenient, for example if you participate in a bounty campaign. Even veterans often forget to move these coins to fresh addresses, too! But it's always a good idea to regularly move coins from re-used addresses to fresh ones.
[2] In theory, once quantum computer technology has advanced to the point where keys can be calculated in less than an hour, even your coins on addresses that were never re-used can be stolen. But first, this would require insane quantum computing power. And second, it's likely that at this date there will always be quantum-safe addresses available.
[3] There are
proposals to burn or re-distribute "vulnerable" coins should quantum computers become a problem. Coins on re-used addresses could be considered "vulnerable". Moving them to an un-used address NOW would save your coins from being burnt because you forget about them in the future!
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