Why there duplicated transactions on the blockchain? (with different hashes)

Question

I just found a couple of transactions that looks very similar, they have different hashes, but are exactly equal in everything else:

3d69534a43b4396faac62e84ba6092d539335dd1c6601da626020f69082280c1 (mempool)

39956e4b81c8c2e8071839cb3d3c92ab2d0f566b0eba9b65474138eec214cd80 (mempool)

Both transactions are on the same block (816,015) and have the same details:

• Size: 312
• Coindays destroyed: 0
• Weight: 561
• Fee: 0.00000546BTC
• Send from: bc1pl2sxa9fujpjk5km840jnqrp5xn57dxezfgsftnqsxaa39x7qkh5sn0k3w3 (‎0,00033681 BTC)
• Received: 3Dvp6Vt5G2xZPP1DDUeSap9MXuLuXY2hpu (0,00000546 BTC)

Those addresses seems to be testing something weird, but I cannot understand what... can someone explain what could be happening there?

Obviously, the main question is how could we be sure that it is not creating new coins, as I cannot understand which output they are spending, as they are using taproot.

Answer 1

Transaction outputs (TXOs) are uniquely identified by their outpoint. Each TXO can only be spent once. While these two transactions spend funds received to the same output script, they are spending different transaction outputs. So, they do not create new bitcoins, they do appear to be creating some BRC20 tokens, though.

Tx 3d69…80c1 spends txo 2821…fe1f:0.
Tx 3995…cd80 spends txo 2821…fe1f:1.

Both TXOs were created by the same preceding transaction 2821…fe1f, which in total created 24 outputs with the same output script (and one change output). The transactions all appear to be minting some BRC20 token.

Answer 2

These are BRC-20 mint transactions.

If you look at any of the inputs, you can see it is a Taproot script path spend that includes an unexecuted branch with several data pushes, the first of which pushes the three bytes 6f7264 (UTF-8 for "ord"). This is what the Ordinals protocol uses for its so-called "Inscriptions", a way to add arbitrary data to the blockchain.

If you look even closer, you may try to decode the last data push as UTF-8:

{"p":"brc-20","op":"mint","tick":"piin","amt":"1000000"}

This is what the BRC-20 protocol uses. BRC-20 is a protocol for creating and transferring tokens on top of Bitcoin. Being as inefficient as it is, it requires a lot of onchain transactions for its operation, which is the main reason for the current spike in Bitcoin's transaction fees (and for the similar spike in May earlier this year).