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I've read through some explanations saying that every client in the network knows every transaction because when someone wants to perform a transaction, he sends that informationen (how much, to whom and his own address) to everybody he knows and everybody they know and every.... and so on. Until it gets confirmed by everybody in the network. Then the transaction can take place. So everybody in the network knows that this transaction happens, and add the new block to their chain.

Does REALLY everybody have the whole history of transactions (a.k.a one HUGE chain of blocks) stored on their (lets say) computer?

Really all? Isn't this amount of bytes too much for normal hard disks (in my computer, smartphone, ...) considering ALL transactions which have ever happened and happen?

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Everyone running a bitcoin Core node must download the entire ledger of transactions listed on the blockchain... But the vast majority of Bitcoin wallets are simply a place that stores a user's private key and allows users to interact with the network. When someone sends a transaction from their wallet, it gets broadcast to the network and eventually to Bitcoin miners.

Once a miner finds the next block (that includes your transaction), the solution gets broadcast to the network and those that are running the full Bitcoin Core software incorporate that block into the blockchain.

So although not everyone needs to download the full bitcoin blockchain, there are still a very large number of people who do, and by doing so, secure the network.

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  • The whole blockchain is encrypted, right? But who got the key?
    – watchme
    Mar 30, 2018 at 11:14
  • The blockchain itself is not encrypted. Actually, it's the opposite... it's all public. What gets encrypted is each person's address and the key is known as your "private key."
    – Nicolas Lopez
    Mar 30, 2018 at 11:19
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    And to your answer: So my bitcoin wallet doesn't store every transaction which has ever happened. But it includes my transaction right? Or does it not include any transaction because all my transactions are added to the one big blockchain there is?
    – watchme
    Mar 30, 2018 at 11:23
  • It's all or nothing. Unless you're running the Bitcoin Core software on a powerful machine (you would know it if you were), your wallet doesn't store any transactions... even your own. The transaction is stored on those running the full BC node. However, your wallet may have some functionality that shows you what coins you've sent and received, but it only does this to help you as a user and isn't necessary for the network to function.
    – Nicolas Lopez
    Mar 30, 2018 at 11:34
  • and those full-nodes check all transactions and do the mining?
    – watchme
    Mar 30, 2018 at 12:03
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Depends on which kind of wallet an user is using.

There are two type of Bitcoin wallets available, classified by the way in which they connect to the blockchain and verify that it is the longest and thus the correct chain to follow:

Otherwise there are SPV wallets:

  • Simplified Payment Verification:

A Bitcoin implementation that does not verify everything, but instead relies on either connecting to a trusted node, or puts its faith in high difficulty as a proxy for proof of validity. BitCoinJ is an implementation of this mode.

MultiBit, Bitcoin Wallet for Android, and Electrum are examples of SPV clients.

some creds to Stephen Gornick

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  • is "node" a synonym for "SVP Wallet" and "full node" a synonym for "Core Wallet"?
    – watchme
    Mar 30, 2018 at 11:50
  • Not a "standard", but I used those terms in the way you are asking. Generally speaking "Full Node" represent the concept of a node with a full blockchain ledger stored locally in a better and more precise way I suppose.
    – user51260
    Mar 30, 2018 at 12:15
  • A full node is a node that verifies everything. Whether it also stores everything is not relevant.
    – Pieter Wuille
    Mar 31, 2018 at 13:36

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