Since Vitalik Buterin developed Ethereum, smart contracts have become an integral part of the blockchain ecosystem. But what is behind these „smart contracts“? In five parts, Ingo Rammer explores the implications of the technology for us. Today: Why is a Smart Contract secure?
Why exactly is the Bitcoin evolution safe?
So far, so good. But what about the security of this approach? What would happen if one of the participants simply exchanged the smart contract on the blockchain node he controlled and used a variant that was advantageous for him like this https://www.onlinebetrug.net/en/bitcoin-evolution/? (Depending on the blockchain, the attacker would have to dive relatively far into the internals of the implementation of the blockchain platform – but it is still a valid attack vector that has to be considered at least on a theoretical level).
What would an attacker have to do?
In our example, an attacker could try to take control of all phone numbers by changing the check conditions in his version of the smart contract. But this would lead to the World State being changed only on the attacker’s node: Only for him it looks as if he controls all telephone numbers.
All other participants would continue to execute the correct version of the contract. If, due to the consensus mechanism chosen between the participants, the attacker is selected by the network itself to generate new blocks, these would immediately be rejected by the other participants.
The attacker would lose the status of the block generator again, since depending on the configuration of the block chain, half or two thirds of all participants must agree with the result of a transaction before it is considered correct network-wide. An attack attempt therefore only harms the attacker himself.
One can therefore compare this attack with a bank customer crossing out the status on his printed account statement and overwriting an increased credit balance. From his point of view, he now has much more money than before. But as soon as he tries to access this money, he is very quickly brought back to the bottom of the facts: his own view remains a wish and will at best be acknowledged by his counterpart with a smile.