How To Get Bitcoin Replay Protection (BTC, XBT)

This is Matthew Crowder's Bitcoin University. Today I want to talk about how to get Bitcoin replay protection for BTC and XBT. In other words, how to protect your Bitcoin from what are called replay attacks. Now, as most of you know, there was a chain split in Bitcoin on August 8th, 2026. And so, there now two versions of Bitcoin. There's Bitcoin on Shaw 256 which goes by the ticker BTC and then there's Bitcoin on Blake 2B which is going by the ticker either XBT or BTC2B. Now the SHA 256 version is completely captured at this point in my opinion and can be controlled by anyone who controls the highly centralized SHA 256 mining cartel. By contrast, the Blake 2B version is a much smaller network and so far lacks many of the powerful network effects that the captured Shaw 256 version still benefits from. But the Blake 2B version of Bitcoin has much better consensus rules, a more robust and decentralized node network, more decentralized mining, and definitely a more cipher punk energy and spirit. So, here are the two blockchains. You can take a look at them. Meool.space space still covers the Shaw 256 blockchain and then meool.guide will give you insight into the Bitcoin on Blake 2B blockchain. Now, these two versions of Bitcoin share common history up until the chain split much like the Lutheran and the Catholics share a common history up until about 1521. You can pick whatever date you want. 1517, 1521, 1530. But much there's a very similar similar thing here where both share common history before the chain splitting and going their separate ways. And this really happened at block height 961632, which was when mandatory signaling was supposed to kick in on the SHA 256 chain. So we can see on the SHA 256 chain block 961632 was mined by Antpool but on the Blake 2B chain it was R it was uh mined by the legendary Rough Necks who proceeded to mine three more blocks and then we had four New York Post blocks and then of course we had the hard fork right here this golden block at 961640 but the real chain split happened right here at 961 632. Now why does any of this matter? It matters because if you held Bitcoin in self-custody going into August 8th when that chain split happened, you probably now also have some Bitcoin on Blake 2B coins, in other words, some XBT that you might not know that you have. If you held, for example, one Bitcoin, one BTC before August 8th, and you haven't moved it since then, you probably now control one B, one Bitcoin, one BTC, Bitcoin on Shaw 256, and one XBT as well, Bitcoin on Blake 2B. So, here's a random example I found on the blockchain. We have this Bitcoin address. This is on the Blake 2B blockchain. We can see it ends in YURW uh JQ and it currently has uh 0.0945 approximately Bitcoin. And the same thing is present on the SHA 256 chain as well. It has the same amount of Bitcoin. And we can see that this UTXO dates from before the chain split of August 8th. The last transaction here was on August 4th of 2026. And likewise on the JH 256 side of things, the last transaction was on August 8th. So this is what I'm sorry, the last transaction here was on August 4th, 4 days before the chain split of August 8th. So this would be an example of a UTXO that exists on both the SHA 256 chain and the Blake 2B chain. It's what we would call a prefork UTXO or unspent chunk of Bitcoin. Now, here's why you need replay protection for pre-fork UTXOs like this. If you do a transaction today that sends your 1 BTC to a new Bitcoin address, your 1 XBT will almost certainly end up getting moved to that new Bitcoin address as well on the Blake 2B chain, of course, because a signed transaction on one of these chains will usually also be valid on the other chain with some exceptions, for example, like having a large operator term. So, if you're sending BTC to yourself, a self a self send or a self- spend, it's not a huge deal because you still control the private keys to that new Bitcoin address where the Bitcoin is going. And so, you can move it on the XBT side or the BTC side if you need to. But where people run into trouble is when they send their BTC to a Bitcoin address that they don't control the private keys to, like an exchange, for example, a Bitcoin exchange or a crypto exchange, because their XBT will then move to that new Bitcoin address as well. And there's no way to get it back unless you can persuade the exchange to send it back. So, here's the scariest thing that can happen. You, let's say you have one BTC valued at $80,000 and one XBT valued currently at about $300. So, let's say you you send that one XBT to an exchange because you're foolish and you want to dump it for fiat, but because you're ignorant of replay protection, your associated one BTC ends up getting sent to the same address at the exchange and then they decide to keep it. Let's say the worst thing happens. So, you basically just lost $80,000 worth of value trying to monetize that $300. So, here's how you can protect yourself from a replay attack like this. Before sending any BTC or XBT anywhere, take a look at what's sitting at that address on both chains at meool.space and mempool.guide as we did right here. You can just enter the address in this box on meool.guide and mempool.space as well. I would do this over the tour browser. uh which you can use uh for sites like these and that way you'll have some privacy or better yet use your own shot 256 or blake 2B node plus the mempool app on start 9 or umbil to view your own instance of mempool.space if you're running shot 256 or mempool.guide guide if you're running Blake2B. That way you won't be associating your IP address with your Bitcoin address, but also using the tour browser for both of these websites uh will give you protection as well presumably. So if you do this, if you type in your Bitcoin address on both of these and it has value on both sides of the chain split, as we saw here, it's worth this isn't converting um to the right dollar amount, but basically 0 uh 0.0945 Bitcoin. And then on the other side on the shot 256 side um we have it as well. So if when you do this for your own Bitcoin address you put it into one of these websites and you're using the tour browser. If your Bitcoin address has value on both sides of the chain split, you're going to need to add something to your transaction to ensure that it doesn't get replayed on the wrong chain. So, let's say you're sending one BTC Shaw 256 Bitcoin out of cold storage over to the river exchange in order to dump it for fiat or maybe because you want to get some fiat so you can buy uh some XBT. Let's say you're sending one BTC over to the river exchange, but you don't want the associated 1 XBT Blake 2B Bitcoin to move over to River as well since the company does not support it. In that case, you need to do this. Buy 0.00001 BTC. In other words, 10,000 SATs from River and then withdraw it onchain to a fresh Bitcoin address in your cold storage wallet. And once it settles in your cold storage wallet, once it's had 3, four, five, six confirmations, go to mempool.guide, which is the Blake2B Bitcoin, do it over tour to make sure that there's no Bitcoin XBT sitting at that address. And if there's no XBT sitting at that address on the Blake 2B side of things, then you're all ready to go because this is a UTXO, a fresh UTXO from River that only exists on the shot 256 side of things. So the next step then is to create a transaction that includes both your 1BTC as well as the 10,000 SATs that you just withdrew from River. It'll now be a little bit less after minor transaction fees were deducted when River sent it to you. Or maybe they allow one monthly free withdrawal. I seem to remember that. But either way, you're basically combining your old old BTC with this freshly purchased BTC. You combine both of those as the inputs and then you send the combined transaction to River to the address, the Bitcoin address they provide and then your BTC or one BTC will move over there. So your transaction again, you'll have two inputs. It'll have your original 1 BTC and then call it uh 9,000 9,000 sats or so that you just withdrew from River. You combine both of those. You have one output which is the Bitcoin address that River gave you for your deposit. So if we take a look at that in a wallet, I'll be using a fork of Sparrow here to show you. We basically have transactions here. You can go down to UTXOs. You can select, let's say this is my one Bitcoin that I was holding in cold storage, my one BTC, which again would be in a different wallet. It would be in the Sparrow wallet uh for all of this as we're going to as we're going to see. But basically, here's my let's pretend this is my my one BTC. And then this is the 9,000 SATs. Hold down the shift key. This is the 9,000 SATs that I just got sent over from River. What I do is I basically select both of those UTXOs. Those will be my two inputs. And then I click send selected. And then I right here in the pay to I would put the River address that I want to send to. And the reason this works is because those freshly purchased SATs, as we saw, don't exist on the Blake 2B side of things. So again, your transaction will have two inputs and one output sending to the river exchange. And this transaction cannot be replayed on the Blake 2B chain because one of the inputs as we said does not exist on the Blake 2B chain and you you know it doesn't exist because you also checked at meool meool.guide. So this transaction cannot be replayed on the Blake 2B chain sending your 1xbt accidentally to river because one of the inputs as we said does not exist on the Blake 2B chain and so your 1 BTC will end up safely on River so that you can dump it while your associated 1 XBT will not move to River. Now, the BEV example assumes that your 1BTC was KYC, that you had given up personal information to the exchange when you bought it. If it was a nonKyc UTXO instead, then you should just buy that 10,000 sats from a peer-to-peer network, a non KYC exchange or something like Robboats instead. Because if you combine a non-KYC UTXO with a KYC UTXO, it makes the former UTXO no longer non KYC because of the common input um ownership heristic. Uh it's quite a bit quite a bit to cover there. I'm covering it covering it quickly. Um but if you're familiar with how non KYC Bitcoin works, you'll you'll understand this. Now, what about if you want to send one XBT to one of the exchanges that supports it, like the Neox X exchange? What if you want to send one XBT there, but you don't want your one associated BTC to also move to NEOX? In that case, all you need to do is buy 10,000 um or 10,000 SATs, the equivalent for XBT from NEOX. Basically doing the same thing we did with River here, but doing it on the XBT side of things. You buy some SATs from NEOX X, withdraw to your XBT wallet and then combine it with your one XBT in a transaction that sends both inputs back to Neox X. And again, that newly purchased XBT, you're going to want to look on on U memple.space to make sure it doesn't exist on the SHA 256 chain. So to summarize, to sort of zoom out, always follow this this overarching principle. In order to avoid having your transaction replayed on the wrong chain, always include something in your transaction that's not valid on the other chain where you don't want your BTC or XBT to move. And so that's what I did with a large OP return in this video. This was my first take on replay protection. You can watch this video. I don't think it's the optimal way to do it, though it can certainly be done where you basically include a large op return so it can't be replayed on the Blake 2B chain. But what I failed to mention in that video is that after RDTS reduce data temporary soft fork, the BIP 110 rules. In other words, after this temporary soft fork expires on Bitcoin on Blake P Blake 2B in September 2027, again, it was a temporary soft fork and it did activate on our chain, even though the mining cartel and the other chain blocked it. But after that expires, I believe it's September 1st, 2027, that large operturn transaction on Shaw 256 that I did in this example, could end up getting replayed on the Blake 2B chain, since it will no longer be prohibited by the RDTS, the BIP 110 rules. So, I think it's best not to use RDTS violations as replay protection, even though some form of RDTS will almost certainly be renewed in some form. Now, one last thing. There is this vicious lie that's being spread by bad actors, which is that Luke Dasher failed to provide replay protection for Bitcoin on Blake 2B for XBT. It's actually the opposite. Bitcoin Core failed to provide replay protection for its own users because it doesn't care about its users, and that's been repeatedly demonstrated. By contrast, though, Bitcoin on Blake 2B comes with full replay protection in the form of Sigash Unified. And so any transaction signed using this cannot be replayed on the Shaw 256 chain. Now you can use the Shrek wallet or the seed signer with Blake 2B firmware to sign transactions using this replay protection using Sigash Unified. I'll be covering this in a future video, but you can read more about it here on the Shrike wallet website which is quite excellent and provides another explanation of replay protection and how you can protect yourself on the Blake 2B side of things with Sigash Unified. Again, the Shrike wallet, which looks like this, is a fork. In other words, a modified copy of the Sparrow wallet. So, if you're familiar with using Sparrow, you'll immediately understand how to use Shrike as well. And I'll be covering more of this in future videos. Basically though, with the Sparrow wallet, you need to use a Bitcoin on Shaw 256 node or public electrum server. That's the equivalent. With a Shrek wallet, you need to be running your own Bitcoin on Blake 2B node to use it. If you'd like a demo of the Shrike wallet in action and more discussion of Bitcoin replay protection, I'll put a link to Greg Tanowski's uh video here, which I encourage you to u to watch and also subscribe to his channel because he's a he's a really smart guy. The whole topic of replay protection, it is a huge topic. So, if you want to do an even deeper dive, I think I've given you enough in this video for you to protect yourself, but if you want to do an even deeper dive that took over two hours, you can also check out the paid live class that I did on it on Saturday on the paid side of things on my website. This was a sea September 19th class, Bitcoin on Blake2B nodes, wallets, and replay protection. So, we did even more there if you want to go a little bit deeper, but I would encourage you before you move any Bitcoin to spend time exploring replay protection and understanding how it works so you don't end up shooting yourself in the foot. And if you'd like to go deeper, I'll put a link to this in the web in the uh description notes below. If you enjoyed this video, be sure to hit the subscribe and like buttons, hit the notification bell if you want to be notified when I publish my next video, and let me know your questions and comments in the comment section below. Thanks a lot for watching and I'll see you in the next