On August 9, Ledger issued a security advisory concerning a potential Bitcoin fork branded as "BIP-110." The warning is precise: the fork lacks built-in replay protection, meaning a transaction signed on one chain can be replayed on the other. This is not a theoretical vulnerability—it is a structural defect that has already cost users billions in previous forks.
Tracing the ledger back to the zero-day exploit, we find a replay attack is the cryptographic equivalent of leaving your keys in the ignition. When a blockchain splits, both chains share the same transaction history and signature scheme. A signed transaction on Chain A is valid on Chain B unless the protocol explicitly prevents it. The fork in question, if it proceeds without a mechanism like SIGHASH_FORKID (used by Bitcoin Cash) or chain-specific OP_RETURN markers, opens every user holding BTC to a double loss: they sign a transaction to claim the fork token, and the same signature moves their original BTC.
Context: The BIP-110 Naming Discrepancy
The term "BIP-110" is historically assigned to the CHECKSEQUENCEVERIFY (CSV) proposal, which was activated on Bitcoin mainnet in 2016 as part of the SegWit soft-fork package. CSV introduced relative timelocks, a feature now integral to Lightning Network and DLCs. The current fork proposal, however, is not a new BIP-110. It is likely a "reversion fork"—a group of miners or developers threatening to run a node version that omits subsequent soft forks (SegWit, Taproot) and then diverging from the main chain. This is a political move disguised as a technical upgrade, and the naming is a deliberate misnomer to invoke legitimacy.
Based on my audit experience, I have seen this pattern before. In 2017, I dissected the Paragon Coin whitepaper and found five contradictions in their consensus claims. The same principle applies here: check the code, not the brand. The fork's technical documentation is absent—no GitHub repository, no client release, no testnet data. The only concrete signal is Ledger's confirmation that its firmware can technically sign the fork's transactions, implying the code exists in some form.
Core: Systematic Teardown of the Replay Attack Risk
Let me walk you through the arithmetic. Assume you hold 1 BTC on the main chain. The fork promises a 1:1 airdrop of the new token. To claim it, you must move your BTC to a new address controlled by the fork's wallet. You sign a transaction on the fork chain. That same signed transaction, if broadcast on the Bitcoin main chain, will transfer your 1 BTC to the same address—but on the main chain, that address is controlled by the fork's developers, not you. Result: you lose your BTC.
The industry has known this risk since 2016. Bitcoin Cash (BCH) solved it by implementing SIGHASH_FORKID, which modifies the signature hash to include a chain identifier. Ethereum Classic (ETC) suffered from replay attacks for months after the DAO fork, with users losing funds on both chains. The proposed BIP-110 fork, according to Ledger, has no such protection. This is not a minor oversight; it is a fundamental failure of security design.
Stress tests reveal what audits cannot. In 2020, I modeled a 40% ETH crash on Compound's liquidation thresholds. The stress test exposed a flaw in collateral factor adjustments that audits missed. Here, the stress test is simple: what happens if a user tries to claim the fork token? The answer is a guaranteed loss of the original BTC unless the user employs complex coin-splitting procedures (e.g., broadcasting transactions with different fee rates or using a coin-specific tool like Electrum's "split" feature). The average hardware wallet user will not do this. The fork is effectively a trap.
Contrarian: What the Bulls Got Right
Some argue that forks can create value. Bitcoin Cash reached $4,000 at its peak, and BSV briefly traded at $500. The narrative is that a fork creates a "free" token that can be sold for profit. However, this argument relies on three conditions: the fork must have replay protection, the fork must be listed on major exchanges, and the market must have sufficient liquidity. The BIP-110 fork fails on all three. Without replay protection, exchanges will not list it—they cannot risk being sued for customer losses. Without exchange listing, the token has no price discovery. The only liquidity channels are peer-to-peer or decentralized exchanges, which are even more vulnerable to replay attacks.
Furthermore, the economic incentive to claim is negative. Even if the fork token has a theoretical value of $100, the risk of losing a $60,000 BTC is a 600x downside. Priors are cheaper than promises. The rational decision is to ignore the fork entirely.
Takeaway: Accountability Call
This is not a novel attack. The industry has known replay protection requirements for nearly a decade. The fact that a fork in 2023 or 2024 still lacks this basic feature signals either incompetence or malice. Audit the code, ignore the cult. If you hold BTC, do not interact with any wallet or address associated with this fork. If you are a developer considering contributing to the fork, ask yourself: why is there no replay protection? The answer will tell you everything.
Metadata does not mint value. A fork without replay protection is not an innovation; it is a liability. The market will price it accordingly—zero. Until the fork provides a documented, peer-reviewed solution for replay protection, the only safe action is to wait and verify before you verify the verifier.
Based on my audit of the Terra Luna collapse, I know that the most dangerous projects are those that ignore the simplest security principles. This BIP-110 fork is a textbook example. The ledger is clear: do not sign.