Monero (XMR) plans to replace ring signatures with FCMP++, a proposed privacy system that its developers say would expand the set of possible transaction senders and address problems with the existing design.
Ring signatures currently obscure a sender's identity. An April 27, 2024, Monero development post says FCMP++ combines Full-Chain Membership Proofs with spend authorization and linkability. The proofs would take over the sender privacy role now handled by rings.
The post points to statistical analysis and difficulties during blockchain reorganizations as reasons for the change. It traces the approach to an earlier proposal in 2023. The developers say the new system would offer senders a larger anonymity set, while some wallet features would be delayed under the proposed design.
The change concerns sender privacy. Monero uses separate tools for other transaction details: stealth addresses protect recipient information, while Ring Confidential Transactions conceal transfer amounts. Those protections provide context for the proposed replacement of rings; the audit request does not describe them as changes to be activated with FCMP++.
An April 6, 2026, proposal by j-berman to Monero's Community Crowdfunding System requests 500 XMR for an integration audit. It divides the work into three phases: FCMP++ Crypto, FCMP++ Curve Tree Building and FCMP++ Consensus Integration.
The proposal treats completion of the final phase as a step toward mainnet readiness. Research review and testing on a beta stressnet are expected to proceed in parallel with the integration work. The request lays out a review process, rather than a date on which the network will adopt the new system.
FCMP++ has not activated on Monero mainnet. The audit proposal gives no activation date, and the project's open upgrade milestone has no due date. Completion of the phased review is the next checkpoint identified in the proposal.
