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I'm reading this article, and quote

The blockchain transaction’s OP_RETURN data can be decrypted using AES-256 GCM to provide a backup command and control domain name

How did someone able to manipulate the Bitcoin transaction script without affecting the transaction?

daisy
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  • Possible duplicate of https://bitcoin.stackexchange.com/questions/29554/explanation-of-what-an-op-return-transaction-looks-like – meshcollider Dec 12 '21 at 03:47

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As I understand it, OP_RETURN allows the script to exit early with a result of FALSE without evaluating the remainder of the script. That means the transaction output is non-spendable but that the whole transaction still passes normal validation tests.

It is designed in a way that allows a small amount of arbitrary data to be embedded in the script.

See

https://bitcoin.org/en/release/v0.9.0#opreturn-and-data-in-the-block-chain says

OP_RETURN and data in the block chain

On OP_RETURN: There was been some confusion and misunderstanding in the community, regarding the OP_RETURN feature in 0.9 and data in the blockchain. This change is not an endorsement of storing data in the blockchain. The OP_RETURN change creates a provably-prunable output, to avoid data storage schemes – some of which were already deployed – that were storing arbitrary data such as images as forever-unspendable TX outputs, bloating bitcoin’s UTXO database.

Storing arbitrary data in the blockchain is still a bad idea; it is less costly and far more efficient to store non-currency data elsewhere.

RedGrittyBrick
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  • If it's not spendable then miners won't include it in the next block(no fees), but it is still searchable in bitcoin transaction explorer, am I right? – daisy Dec 12 '21 at 14:20
  • There are still transaction fees even though one of the outputs of the transaction is unspendable (there is no recipient). So it will be included in a block. – RedGrittyBrick Dec 12 '21 at 19:11
  • Understood, the unlocking script is fine, and the locking script is verified in the next transaction, so it won't affect the current transaction. – daisy Dec 13 '21 at 04:21