The core team behind Bitcoin has officially added a new proposal, titled Pay-to-Merkle-Root (P2MR), to the project’s Bitcoin Improvement Proposal (BIP) repository. Although the development quickly grabbed the attention of the crypto community, no Bitcoin node has yet implemented the P2MR feature, and developers have yet to announce a timeline for its deployment.
How P2MR Compares to Taproot
P2MR is being described as a streamlined alternative to the current Taproot output, known as P2TR. Taproot typically allows users to spend their funds through two main routes: either using a direct signature in the key-path or revealing a script with a Merkle proof via the script-path. Most Taproot transactions favor the key-path because it is smaller and less costly. P2MR, by contrast, eliminates the key-path entirely, linking outputs directly to the Merkle root of a script tree. As a result, every spend with P2MR requires disclosure of the corresponding script and submission of a Merkle proof. This design means P2MR outputs are larger—at least 103 bytes—and come with higher transaction fees than Taproot.
Quantum Computing Risks and Attack Scenarios
Discussions on potential threats from future quantum computers have become increasingly relevant, particularly if an extended attack window appears through on-chain data. The newly published BIP-0360 examines quantum risk through two main attack models. In long-term attacks targeting publicly visible keys that remain on-chain for years, advances in quantum computing could eventually allow offline attempts to derive private keys. In short-term attacks, the attacker must obtain the private key before a pending transaction is confirmed—a far tougher feat. P2MR is aimed at mitigating these long-duration quantum threats, though it offers only limited protection against short-term attacks.
Activation Process and Transition Challenges
Major changes to the Bitcoin protocol, such as P2MR, undergo a slow, carefully coordinated rollout. The BIP-0360 proposal is still early in this process; widespread adoption would require passing through several stages. Should the proposal be activated, wallets would begin supporting a new P2MR address format—possibly starting with “bc1z”—allowing users to send funds using a format designed to reduce long-term quantum risks. However, Taproot outputs would remain spendable, and the new protection would not cover previously created Taproot transactions.
Migration to P2MR is intended to be opt-in rather than automatic. Users prioritizing this added layer of security will have the option to switch voluntarily. While this may appeal to large holders and custodial institutions seeking long-term assurance, it could be less attractive for everyday users due to bigger transaction sizes, higher fees, and some privacy trade-offs.
A broad consensus across network stakeholders—node operators, miners, developers, and economic actors—will be essential before any network-wide activation. Moreover, the long-term relevance of P2MR will hinge partly on future standards for post-quantum digital signature algorithms and how these can be integrated with Bitcoin’s protocol.
On the technical side, P2MR is intended to serve as a new building block that preserves much of the flexibility introduced by Taproot. The design’s scope includes advanced scripting for applications such as multisignature solutions, time-locked vaults, and smart contracts.
Isabel Foxen Duke, one of the proposal’s co-authors, has emphasized clarity in presenting the technical aspects—not just for Bitcoin core developers, but for the wider public as well. This strategy aims to make quantum-readiness an accessible, comprehensible concept for anyone in the Bitcoin ecosystem.
Recent academic research in cryptography is also beginning to provide clearer forecasts about post-quantum signature methods and the actual capabilities of quantum computers. Despite this growing body of knowledge, it will take years of community debate, development, and rigorous testing before a decision is made on integrating P2MR into Bitcoin’s main protocol.
