How Cold Storage Wallets Work:
A cold storage wallet doesn’t have just 1 address, what you really have is a master key system.
Your 12 or 24 word seed phrase is the master key to all your addresses. That seed mathematically generates a master private key snd master public key.
Your private key controls your Bitcoin and your public key generates all your addresses. And your wallet uses the private key to sign transactions.
Your wallet has a XPUB which mean extended public key. It’s like a view only master key.
It allows you to generate all your receive addresses, track balances, and build the full tree of addresses.
So your seed phrase gives you full control, your private key spends funds, and your XPUB sees everything and generates addresses but cannot spend.
Modern wallets use something called HD wallets (Hierarchical Deterministic Wallets). It means that all addresses are derived from the same seed and your wallet creates a new address for every transaction.
This means you can have thousands of addresses for each time you receive Bitcoin and they’re all tied to the same seed.
This is done for privacy. If you just had 1 address anyone could track your entire balance.
So there is a branching structure to wallets. Where the master seed is at the top and your receiving addresses and change address are branched underneath it. (Change addresses are where your change is sent when the leftover bitcoin (change) is sent back to you after you send Bitcoin somewhere)
Finally the way to think of it easily is:
Seed phrase - Master root (controls everything)
From it - You have infinite private/public key pairs
From those - you have infinite addresses
XPUB - lets you see all branches without control.
If someone gets your seed phrase it’s game over and they can take everything.
If your XPUB is leaked they can track everything you have in all your wallet addresses.
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