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I thought one safe way to keep a bitcoin "cold" and safe is to not show its address ever to the public.

However, let's say if I create an address, so that means I create a pair of public and private key, and then the public key can go through some steps to become an "address".

Now, if I deposit 0.001 bitcoins from Coinbase or Coinbase Pro into my mobile wallet (or any wallet), isn't it true that the Ledger (the blockchain) has to have a record of

 Transfer of bitcoin from Address 123c6...e6.  to   987a1...39   Quantity: 0.001

So somehow, that new address has to be "public" because it is in the blockchain and anybody can see it? So how would it be possible to have an address and be able to deposit some bitcoin into it without showing the address to the public?

nonopolarity
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2 Answers2

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I thought one safe way to keep a bitcoin "cold" and safe is to not show its address ever to the public.

Cold storage = Private keys offline

So somehow, that new address has to be "public" because it is in the blockchain and anybody can see it? So how would it be possible to have an address and be able to deposit some bitcoin into it without showing the address to the public?

Yes blockchain will have all transactions and UTXOs. It is possible to avoid being associated with the addresses on blockchain. So even if I see an address with 0.1 BTC unspent and some transaction, I don't know who owns it and who was involved in the transaction.

  • I think what you are saying is, in order that my address has 0.001 bitcoins, I will need to show this address to the public. But it is just that I never use this private key in some untrustworthy systems such as a mobile wallet that can be hacked. So I use this private key only on very secure system and as little as possible, and once the 0.001 bitcoins is in this address, I take this private key offline, and supposedly, 10 years later, nobody should have "cracked" my private key and stole the 0.001 bitcoin in this address – nonopolarity Feb 01 '21 at 13:07
  • You can sign the transactions on an offline system and broadcast this signed transaction from elsewhere (online device). So that private keys always remain offline. –  Feb 01 '21 at 13:23
  • interesting... have some offline system, and then sign it... and then perhaps generate the signed transaction into some kind of QR code, and then let my smartphone scan that QR code... this way, my private key is never "connected to the world". I just have to worry my private key might be embedded in the QR code by some malware... or I guess it is possible to generate that signed transaction as a string... and I just have to type it into an online computer – nonopolarity Feb 01 '21 at 13:49
  • Signed transaction does not contain 'private key'. Signing of transaction is explained in this answer: https://bitcoin.stackexchange.com/a/99791/ and signed transaction will be in the form of hex similar to the one mentioned in this answer in the end: https://bitcoin.stackexchange.com/a/99112/ –  Feb 01 '21 at 14:01
  • I know, signed transaction does not contain private key. With the private key, somebody can get the bitcoin of that corresponding "address". What I meant was if there is a malware that put it in the QR code without the owner knowing it – nonopolarity Feb 01 '21 at 14:19
  • Yes you should follow the best practices and ensure offline device has no malwares. Some of the best practices that I can suggest: Open source OS (Some Linux distro), Not used for anything else or keep a virtual machine only for bitcoin cold storage, Open source bitcoin wallet with active development : either compile yourself from source or download from original source and verify authenticity before use. –  Feb 01 '21 at 14:28
  • if the virus is good, it can really go into the VM and get the private key... unless if you encrypt it on the VM. And even if I buy a MacBook Air to be offline and store my bitcoin, how do I know 5 years from today, it can still boot up without any issue -- and not risk losing all bitcoins. I guess I have to have backup as well... it is such a giant task to keep my bitcoin safe – nonopolarity Feb 01 '21 at 15:11
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For all the researches I have done so far, the blockchain contains all the info about which address has how many bitcoins. All the blockchain info is public.

So the address, when it already is associated with some bitcoin, cannot be unknown to the public.

nonopolarity
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