Cross-chain Rebase Token

A cross-chain rebase token protocol where users deposit ETH into a vault to mint RBT 1:1; balances grow linearly over time based on a per-user snapshot rate, and CCIP bridging burns/mints while preserving that rate across chains.

Features

• Dynamic Balance: The balanceOf function is dynamic to show the increasing balance with time
• Linear Growth: Balance increases linearly with time
• Action-based Minting: Mint tokens to users every time they perform an action (minting, burning, transferring, or bridging)
• Individual Interest Rates: Each user gets an individually set interest rate based on the global interest rate at the time of deposit
• Early Adopter Rewards: Global interest rate can only decrease to incentivize/reward early adopters
• Token Adoption: Designed to increase token adoption

How it works

• Vault deposits and redemptions: Users deposit native ETH into Vault, which mints RebaseToken 1:1 at the current global interest rate snapshot for that user. On redemption, the token is burned and ETH is returned.
• Per-user interest snapshots: On first mint (via deposit or inbound bridge), the user receives a personal interest rate equal to the then-current global rate. That personal rate stays fixed for that user and is used for all future accrual.
• On-demand interest materialization: Actual token supply growth is materialized on actions (mint, burn, transfer, bridge). Before each action, accrued interest since the last interaction is minted to the user via _mintAccruedInterest.
• Cross-chain via CCIP: When bridging, the source RebaseTokenPool burns tokens and forwards the sender’s personal interest rate to the destination pool, which mints the same amount to the receiver and sets their user rate to match.

Interest math

• Balance is computed as: balance = principal * (1e18 + userRatePerSecond * timeElapsed) / 1e18.
• The initial global rate is 5e10 (≈ 5e-8 per second). The global rate can only decrease. New depositors inherit the current (potentially lower) rate.
• On transfers, if the recipient has a zero balance, the recipient inherits the sender’s user rate on first receipt.

Contracts

• src/RebaseToken.sol: ERC20 with rebase logic, per-user interest snapshots, and MINT_AND_BURN_ROLE used by trusted actors (vault and pool).
• src/Vault.sol: Holds ETH. deposit() mints RBT 1:1 at the current global rate snapshot. redeem(amount) burns tokens and sends back ETH. Supports type(uint256).max to redeem full balance.
• src/RebaseTokenPool.sol: Chainlink CCIP-compatible TokenPool that customizes:
  • lockOrBurn: burns tokens and encodes the sender’s per-user rate into destPoolData.
  • releaseOrMint: decodes destPoolData and mints to the receiver with the same per-user rate.

Deployed Contracts

ZKsync

• Rebase Token Address: 0xCce3aa8C657ccC5B9Af3037C9dD2DFFFEABdE889
• Pool Address: 0x68dd6a0195b2588e05C87Be1e2643137658c9D79

Sepolia

• Rebase Token Address: 0xd4Cfe90b37520B542ae259fcb522513c83A34ac8
• Pool Address: 0xB8fBF532e20316372a355B6f70c53B2089dDb627

CCIP Transactions

• Explored Hash: 0x4a293190ac060bef8753298445367470e1a4a3481272d6f211a7f3bfc37d5bd0

Chainlink CCIP roles and setup

• Token admin (CCIP Token Admin): Owns token ↔ pool configuration.

  1. Register admin via token owner: RegistryModuleOwnerCustom.registerAdminViaOwner(token)
  2. Accept admin role: TokenAdminRegistry.acceptAdminRole(token)
  3. Set the token's pool: TokenAdminRegistry.setPool(token, pool)

• MINT_AND_BURN_ROLE on the token: Granted to trusted actors that need to mint/burn:

  • Vault (mints on deposit; burns on redeem)
  • RebaseTokenPool (burns on source chain; mints on destination chain)

• Router and RMN: RebaseTokenPool takes CCIP router and rmnProxy. In tests/scripts we fetch them from CCIPLocalSimulatorFork.getNetworkDetails(block.chainid). On real networks use production addresses from Chainlink docs.

• Chain allowlisting: Use TokenPool.applyChainUpdates to allow a remote chain, set the remote pool/token addresses, and configure rate limiters.

Getting Started

Prerequisites

• Foundry (forge/cast)
• RPC URLs for your target chains (e.g., Sepolia, Arbitrum Sepolia)
• LINK on source chain for CCIP fees

Install dependencies

make install

Installs:

• OpenZeppelin Contracts v5.4.0
• Chainlink CCIP v2.17.0-ccip1.5.16
• chainlink-local v0.2.5-beta.0 (for CCIPLocalSimulatorFork)

Run tests

forge test -vvv

Local CCIP simulation (multi-fork)

• test/CrossChain.t.sol spins up Sepolia and Arbitrum Sepolia forks, deploys token, pool, vault, registers CCIP Token Admin, sets pool, configures lanes, then bridges tokens end-to-end.

Deployment and configuration

Scripts use Foundry forge script.

1) Deploy token and pool

forge script script/Deployer.s.sol:TokenAndPoolDeployer \
  --rpc-url $RPC_URL \
  --broadcast

2) Grant token role to the pool

forge script script/Deployer.s.sol:SetPermissions \
  --sig "grantRole(address,address)" \
  <TOKEN_ADDRESS> <POOL_ADDRESS> \
  --rpc-url $RPC_URL \
  --broadcast

3) Register CCIP Token Admin and set pool

forge script script/Deployer.s.sol:SetPermissions \
  --sig "setAdmin(address,address)" \
  <TOKEN_ADDRESS> <POOL_ADDRESS> \
  --rpc-url $RPC_URL \
  --broadcast

4) Deploy vault and grant role

forge script script/Deployer.s.sol:VaultDeployer \
  --sig "run(address)" <TOKEN_ADDRESS> \
  --rpc-url $RPC_URL \
  --broadcast

5) Allowlist a remote chain and pool

forge script script/ConfigurePool.s.sol:ConfigurePool \
  --sig "run(address,uint64,address,address,bool,uint128,uint128,bool,uint128,uint128)" \
  <LOCAL_POOL> <REMOTE_CHAIN_SELECTOR> <REMOTE_POOL> <REMOTE_TOKEN> \
  <OUTBOUND_ENABLED> <OUTBOUND_CAPACITY> <OUTBOUND_RATE> \
  <INBOUND_ENABLED> <INBOUND_CAPACITY> <INBOUND_RATE> \
  --rpc-url $RPC_URL \
  --broadcast

6) Bridge tokens via script

forge script script/BridgeTokens.s.sol:BridgeTokens \
  --sig "run(address,address,uint64,uint256,address,address)" \
  <RECEIVER> <ROUTER> <DEST_CHAIN_SELECTOR> <AMOUNT> <LINK_TOKEN> <TOKEN_TO_SEND> \
  --rpc-url $SRC_RPC_URL \
  --broadcast

Development

• Update global interest rate (owner-only, can only decrease): RebaseToken.setInterestRate.
• Users inherit their rate on first mint or first receipt if balance was zero.
• Use principalBalanceOf(user) to read minted amount excluding accrued interest.
• Vault.redeem(type(uint256).max) redeems full balance.

File map

• src/RebaseToken.sol: ERC20 + rebase logic and role-gated mint/burn
• src/Vault.sol: ETH vault, deposit/redeem flows
• src/RebaseTokenPool.sol: CCIP TokenPool adapter with user rate propagation
• script/*.s.sol: deploy, permissioning, pool configuration, bridging
• test/RebaseToken.t.sol: unit tests for vault and token logic
• test/CrossChain.t.sol: end-to-end multi-fork CCIP bridge test

License

MIT