On-chain Message: A Unique Communication Method of the Bitcoin Network

In recent years, on-chain messaging has been frequently used as a special means of communication in the blockchain world during various security incidents. For example, a certain security team was able to communicate multiple times with attackers through on-chain messages, ultimately successfully facilitating the return of all stolen funds. In an anonymous environment, on-chain messaging can serve as an effective tool for establishing initial dialogue, laying the groundwork for subsequent fund recovery.

The Bitcoin network supports on-chain messaging, and its implementation mainly relies on the OP_RETURN instruction. This instruction allows users to embed 80 bytes of custom data in transactions, which will not be used by nodes for transaction validation and will not affect the UTXO state; it is purely for recording information and will be fully recorded on the blockchain.

How to Use OP_RETURN for on-chain Messaging

Step 1: Encode the message content

First, the text information needs to be converted to hexadecimal (HEX) format. For example, the HEX of "This is a test." is: 54686973206973206120746573742e

You can use online format conversion tools or implement it through programming. Note that the message content must be less than 160 hexadecimal characters (i.e., 80 bytes). If it exceeds the length, it is recommended to simplify the information or send multiple messages.

Step 2: Build a transaction with OP_RETURN

Next, you need to use a Bitcoin wallet or tool that supports custom transactions to create a transaction with an OP_RETURN output. Taking a certain wallet as an example, you can enter the hexadecimal information in the dedicated input box in the "Advanced Mode" on the transfer interface.

Step 3: Broadcast the transaction

Broadcast the signed transaction through the Bitcoin network. Since OP_RETURN transactions do not actually transfer funds, a miner's fee must be included to be processed. Once confirmed by the miners and packaged into a block, the message will be permanently stored on the Bitcoin blockchain.

Step 4: Check the message content

After completing the transaction, you will receive a TXID, which can be viewed through a block explorer. The explorer usually automatically decodes the OP_RETURN hexadecimal data back to ASCII, making it easier for users to view the actual message content.

Applications of OP_RETURN

In security incidents, OP_RETURN is often used in the following scenarios:

1. The attacker actively expresses the intention to return the funds.
2. The project team and the security team reached out to the attackers, trying to establish contact.
3. As a "tagging" operation, such as tagging suspicious addresses.

A striking case is that, on the eve of an international conflict, an anonymous user utilized OP_RETURN to leave on-chain messages, marking nearly 1000 addresses suspected of being linked to a certain country's security agency. These messages directly indicated that these addresses might be involved in cyber attacks or espionage activities. It is worth noting that when the user published these warnings, they also burned a significant amount of Bitcoin, attracting widespread attention.

Summary

On-chain messaging, especially the OP_RETURN in the Bitcoin network, provides an anonymous, public, and immutable way of communication, playing an important role in the early stages of fund recovery contact and information dissemination. However, users need to remain vigilant when using this feature to avoid becoming targets of attackers. In the event of a security incident, it is recommended to seek assistance from a professional security team in a timely manner to improve the success rate of fund recovery. At the same time, continuously strengthening security awareness is crucial for both users and project parties.