I'm new to the cryptocurrencies world and I'm trying to understand how all this stuff works, so expect a really noob question.

Suppose there's a user which generates a number of addresses and sets up his private blockchain. One of this address will start illegal transactions moving money that doesn't really exist. Since the other nodes of the network are controlled by him, the transaction will be validated. Now this address is moved from his private blockchain to a public pool.

How does the blockchain knows/prevents the malicious node from spending money that are not really there?

Thank you!


2 Answers 2


The blockchain will only accept blocks which are based on previously accepted blocks and have a hash value that satisfies the current difficulty requirements. A malicious attacker is in the same position as any other miner, so any block that he mines must satisfy the same conditions regarding validity. In fact, the bitcoin protocol is designed to be trustless, which means that even miners with malicious intentions are not able to destroy its integrity unless they manage to control a majority of the mining power.


I think of the individual bitcoins as all already existing, as opposed to being mined into existence by miners. There are 21 million. Period. Each “bitcoin/satoshi” has it’s own identification tag, say. What miners do is release them, sequentially (the very last one in the year 2140 or so due to the halving every four years); and as payment- for the “work” of adding the next block (or ledger entry) to the long ledger of transactions of other coin movements (the chain) -these miners are then the custodian of those newly released coin’s tags via an address that the miner controls with a key… until they are spent, when that happens, another miner (presumably) will be the one to record the movement or transference of those “tags” as they become under the custody of someone else (ie. the payee). The address they get put “in,” say, is accessible if you know the key (ie. A bunch of random words in a specific sequence). So when the chain is transparent to all, it translates to not having any duplicates or double spends. Think of the way mailboxes at the post office are all accessible/transparent on the mailman/woman’s side, but require keys on the public side(in a roundabout sort of way). The only way to corrupt the process or to alter which tags are currently custodies of which addresses would be to control more than half of the participating ledgers (miners/nodes) putting it in disagreement with the other half of the ledgers.

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