user58426: I'm pretty sure that I understand how replay attacks work:
A malicious node takes a valid transaction from chain A, and replays it on chain B. Other nodes on chain B see the transaction as valid and therefore it is included in both chains, instead of just A.
My question is whether the first transaction in a block, that generates new bitcoins, can be also replayed.

user5292: Short answer: No.
Longer answer: depends on the rules of the B chain.
A coinbase transaction creates coins out of thin air, but is typically only valid if the block itself is valid. Typically if the block is valid on chain A it's not valid on chain B: because a block usually points to it's previous block, which should be on the same chain.
On the other hand, the rules of B chain can literally be anything, as crazy as the creators imagination allows. If the B chain is specifically designed to also allow A blocks, then the answer would be yes. But the coins would still belong to the miner, so it's hardly an attack.

58426: <p>I'm pretty sure that I understand how replay attacks work:
A malicious node takes a valid transaction from chain A, and replays it on chain B. Other nodes on chain B see the transaction as valid and therefore it is included in both chains, instead of just A.</p>

<p>My question is whether the first transaction in a block, that generates new bitcoins, can be also replayed.</p>
 5292: <p>Short answer: No.</p>

<p>Longer answer: depends on the rules of the B chain.</p>

<p>A coinbase transaction creates coins out of thin air, but is typically only valid if the block itself is valid. Typically if the block is valid on chain A it's not valid on chain B: because a block usually points to it's previous block, which should be on the same chain.</p>

<p>On the other hand, the rules of B chain can literally be anything, as crazy as the creators imagination allows. If the B chain is specifically designed to also allow A blocks, then the answer would be yes. But the coins would still belong to the miner, so it's hardly an attack.</p>
