Zero-Fee USD₮ Transfers

Plasma enables gasless stablecoin payments using a protocol-managed paymaster system for USD₮. This design removes fee friction for users, simplifies integration for developers, and avoids the need for third-party relayers or gas token routing. The system is scoped tightly: it sponsors only direct USD₮ transfers, with identity-aware controls to prevent abuse and a planned blockspace reservation model for predictable inclusion.

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How it Works

Plasma maintains a dedicated paymaster contract that allows verified users to send USD₮ without holding XPL. The system is simple to adopt, wallet-agnostic, and enforced by protocol-operated logic.

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1. Paymaster Contract

The core of the system is a non-general-purpose paymaster built around a single rule: sponsor only verified USD₮ transfers.

• Scoped to transfer() and transferFrom() calls to the official USD₮ token
• Validates eligibility based on verification status and rate conditions
• Covers gas costs using a pre-funded XPL balance from the Plasma Foundation

The paymaster is isolated by design. It does not allow arbitrary calldata passthrough or generalized transaction sponsorship.

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2. Identity Verification

To prevent spam or Sybil abuse, users must complete lightweight identity verification before accessing fee-free transfers. We are actively evaluating multiple options for this layer, including:

• zkEmail or zkPhone-based attestations
• Cloudflare Turnstile or Friendly Captcha
• Signature-based allowlists with expiration

These systems are offchain but privacy-preserving. Verifications can be stateless, appended to the user operation, and verified by a public root or contract without linking identity to onchain state.

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3. Rate Limits

Usage is capped per wallet to ensure fair access and cost control. Limits may be enforced as:

• A rolling cap on subsidized USD₮ transfers (e.g. 5 per 24 hours)
• A gating condition inside the paymaster that checks wallet history or sponsorship frequency

We are evaluating whether this logic will live fully onchain or use a hybrid model with checkpoints. Enforcement will be deterministic and transparent, whether through contract storage or signature-bound counters.

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4. Reserved Blockspace (Planned)

To guarantee predictable inclusion under congestion, Plasma is exploring a priority blockspace model changing Reth’s block building logic. This would involve:

• Tagging eligible USD₮ transfers routed through the paymaster
• Segregating them into a dedicated mempool or mempool subset
• Modifying Reth’s block builder to reserve part of the block’s gas for tagged transactions

During block construction, this reserved gas would be allocated first to eligible transfers, ensuring timely inclusion without competing on fees. If the blockspace is unused, it can fall back to general use. This is a potential path for deeper integration into Plasma’s execution layer. It would require changes to the EVM logic but enable meaningful improvements to block inclusion guarantees. This mechanism is not required for the first release but is being explored for future upgrades.

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5. Wallet Compatibility

Any EVM compatible wallet can support gasless USD₮ transfers without modification. The paymaster system is compatible with:

• EIP-4337 smart contract accounts
• EIP-7702 flows for upgraded EOAs
• Standard wallets integrating with paymaster-aware bundlers

No protocol-specific SDKs or wallet forks are required. Wallet partners will be able to display eligibility, usage limits, and fallback behavior directly in the UI.

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Funding and Economics

The paymaster is funded by the Plasma Foundation. Gas costs are covered at the moment of sponsorship not reimbursed after the fact. Users never need to hold XPL or pay upfront. The system does not mint or reward anything. Subsidies are:

• Transparent and observable
• Spent only when real USD₮ transfers are executed
• Controlled by verification and rate limits

Future upgrades could enable gas-based validator revenue to fund the system, but the initial rollout is directly supported by the foundation.

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Why this Matters

Stablecoin transfers are the core use case on Plasma. But fee friction limits adoption, especially in high-frequency or low-value flows. By offering fee-free USD₮ transfers as a chain-native feature, Plasma can:

• Improve UX without wallets needing gas tokens
• Enable smart contract adoption in emerging markets
• Make stablecoin flows viable for messaging, micropayments, and commerce

This system works without breaking EVM standards, requiring new wallets, or introducing hidden complexity.

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What to Expect

Zero-fee USD₮ transfers will launch shortly after mainnet beta. The initial release will include:

• A protocol-operated EIP-4337 paymaster
• Lightweight identity verification for eligibility
• Integration examples and testnet access for wallets and developers

Future upgrades may add support for additional stablecoins, deeper block building integration, and enhanced tooling.