BIP-360 Proposes P2MR to Mitigate Future Quantum Risk
On March 10, 2026, Bitcoin developers officially placed quantum resistance on the network's long-term roadmap with the publication of Bitcoin Improvement Proposal 360 (BIP-360). The proposal introduces a new transaction output type called Pay-to-Merkle-Root (P2MR), which directly addresses a key vulnerability in Bitcoin's current structure. The primary threat from quantum computers targets public-key cryptography, such as the Elliptic Curve Digital Signature Algorithm (ECDSA) and Schnorr signatures used by Bitcoin, which could be broken by a sufficiently powerful machine. P2MR mitigates this by removing the "key path" spending option available in Taproot transactions. This option exposes a public key when used, creating a potential future attack vector. Instead, P2MR forces all transactions to use a "script path," which relies on hash-based commitments that are significantly more resilient to quantum attacks.
Upgrade Preserves Scripting but Increases Transaction Size
While BIP-360 removes the convenient key path spending option, it fully preserves Bitcoin's smart contract capabilities. All complex functions—including multisig setups, timelocks, and advanced custody solutions—remain available through Tapscript Merkle trees. The primary trade-off is a marginal increase in transaction size and, consequently, slightly higher transaction fees compared to a Taproot key path spend. This is a deliberate exchange of cost-efficiency for long-term security. However, BIP-360 is not a complete post-quantum solution. It does not replace the underlying cryptographic signature schemes, nor does it automatically protect existing unspent transaction outputs (UTXOs). Users would need to proactively move their funds to new P2MR-style addresses to gain the enhanced security.
Ecosystem Faces Multi-Year Adoption Path for Quantum Hardening
The proposal marks the beginning of a multi-year effort that will require coordinated updates across the entire Bitcoin ecosystem. For BIP-360 to be effective, wallets, exchanges, custodians, and hardware manufacturers must all integrate support for the new P2MR address type, which may use a new prefix like "bc1z." This gradual adoption mirrors previous major network upgrades such as SegWit and Taproot. By acting now, developers are preparing for a threat that is still considered years or decades away, following the principle that critical infrastructure migrations require extensive lead time. This proactive stance aims to ensure Bitcoin can transition smoothly to a post-quantum standard before any cryptographically relevant quantum computer becomes a reality.
