This issue is important, as Luke Dashjr and other proponents of BIP-110 discuss a hard fork that would replace the SHA-256d mining algorithm in the minority chain with BLAKE2b. This move would create an entirely new architecture, but both networks would still share the transaction history accumulated before the split.
What is a Replay Attack?
Imagine someone has 1 Bitcoin before the hard fork. When the blockchain splits, the same historical unspent transaction output (UTXO) exists in both networks. In practice, the owner controls the corresponding coins in each chain using the same private key.
Problems begin if both networks also recognize the same transaction and signature rules. Suppose the owner sends a coin to an exchange on chain A. If this signed transaction is also valid on chain B, another party can copy it and broadcast it on that chain. Chain B may accept the transaction because cryptographically, nothing distinguishes this authorization from one intended for its network.
This is a replay attack. No one is stealing a private key or hacking Bitcoin's cryptography. The problem is simpler: the user created one valid authorization, but two blockchain networks recognize it. And while the BIP-110 chain is at block height 961636, people spending BTC are simultaneously moving BIP-110 coins — or whatever they might be called in the future — without even realizing it.
"The overwhelming majority of these [BIP-110 minority chain] blocks simply replay transactions made days ago on the main chain," wrote Mempool.space developer Mononaut on X. The topic of replay protection or replay attacks has sparked intense discussion on X over the past few days.
Replay Protection Builds a Wall Between Chains
Replay protection prevents such crossover by making transactions in competing networks distinguishable. One method involves changing the signature hash, commonly called sighash, so that a transaction signed for one chain does not match the consensus rules of the other.
Mandatory protection makes this distinction part of the fork itself. Optional protection leaves normal transactions potentially compatible with both chains and requires users to consciously use a chain-specific mechanism when they wish to split their coins.
This distinction has become important for BIP-110. The emerging plan apparently does not include automatic and comprehensive two-way replay protection. Instead, at least based on Discord discussions, Bitcoin Knots is implementing a new sighash variant that can create transactions valid on the RDTS chain but invalid on Bitcoin Core.
Dashjr Claims Protection is the Other Chain's Problem
Dashjr has taken an unusual position regarding which network should be responsible. On August 18, responding to a question about replay protection for the proposed hard fork, he said: "Replay protection was the responsibility of Spamcoin, as it's an altcoin being airdropped."
He added that ways would be found to split transactions but argued that "legitimate Bitcoin transactions should remain valid on the Bitcoin network." His reasoning is based on the assertion that the BIP-110/RDTS minority network is part of Bitcoin, while the overwhelmingly dominant Bitcoin blockchain on SHA-256d is the forked-off network.
Dashjr has repeatedly used derogatory names for the dominant Bitcoin chain, including "Spamcoin" and "Bpedo" — a term incorporating "pedo." He has characterized this network as an altcoin while continuing to describe the BIP-110 branch as legitimate Bitcoin.
Network Numbers Tell a Very Different Story
This characterization contradicts observed network activity. BIP-110 miner signaling peaked at approximately 2.53%, and when that branch's consensus rules activated on August 8, its minority chain produced only two blocks immediately after launch before stalling. The dominant Bitcoin chain continued functioning while the gap widened by hundreds of blocks. A few more BIP-110 blocks have been mined at an extremely low rate.
The majority network retained virtually all of Bitcoin's significant hash rate, the longest chain, proof-of-work weight, liquidity, and economic adoption. Subsequently, the BIP-110 proposal was considered closed, with its supporters moving to plans for a proof-of-work (PoW) algorithm change to BLAKE2b aimed at reviving the minority network.
Furthermore, the Bitcoin community is annoyed by Dashjr's repeated claims, and the debated "opt-in" replay protection is a point of contention. "Lol. Luke isn't going to launch his shitcoin without replay protection, is he? I guess it won't get listed on exchanges then," wrote one X user on Wednesday.
Another X user countered:
"This has crossed the line from nonsense to malicious behavior. Spreading this kind of misinformation can cause real financial harm to bitcoiners."
Opt-in Protection Places Burden on Users
According to the approach currently being discussed on the Bitcoin Knots Discord channel, normal transactions may remain vulnerable to replay, as RDTS intends to maintain compatibility with existing Bitcoin Core sighash types. Users wishing to avail themselves of RDTS-specific protection would need to use a new sighash, requiring support from wallet software or hardware signing firmware.
Users could also attempt to split their coins manually. A Bitcoin transaction containing data that RDTS rejects could create an output existing only on the dominant chain. Conversely, the proposed RDTS-specific sighash could result in a transaction that RDTS accepts but Bitcoin Core rejects.
The result more closely resembles optional, opt-in replay protection than the automatic "firewall" users might expect from a contentious hard fork. Consequently, wallets, exchanges, and crypto holders would need to determine on their own precisely which transactions could bleed between chains. This arrangement seems odd, especially for a new chain and crypto asset with no exchange support. Infrastructure providers, particularly crypto exchanges, are unlikely to deal with a chain that prefers opt-in protection over a universal barrier against replay.
If the BLAKE2b fork occurs around September 1st, replay protection will be more than just an obscure technical detail. It will be a practical test of whether users can safely separate assets inherited from the same Bitcoin history, even as Dashjr continues to claim that the network accounting for virtually all of Bitcoin's hash rate, liquidity, and economic activity is somehow an altcoin.
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