papers/lux-teleport-architecture/sections/03-teleporter-contract.tex

\section{Teleporter Contract}

\label{sec:teleporter}
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The Teleporter is a chain-agnostic contract that implements the wire protocol. One audited Solidity implementation is deployed across all EVM chains. Non-EVM chains receive functionally identical implementations in their native languages, each tested against the same conformance suite (\S\ref{sec:conformance}).

\subsection{Contract Interface}

\begin{lstlisting}[language=Solidity,caption={Core Teleporter interface (simplified)}]
interface ITeleporter {
    // User-facing
    function deposit(
        address token,
        uint256 amount,
        uint64  dstChainId,
        bytes32 recipient
    ) external;

    function withdraw(
        bytes32 tag,    // RELEASE only
        uint64  srcChainId,
        uint256 nonce,
        address token,
        address recipient,
        uint256 amount,
        bytes   calldata proof
    ) external;

    // MPC-submitted
    function submitBacking(
        address token,
        uint256 backing,
        uint256 timestamp,
        uint64  srcChainId,
        bytes   calldata proof
    ) external;

    function submitYield(
        address token,
        uint256 newSharePrice,
        uint256 epoch,
        uint64  srcChainId,
        bytes   calldata proof
    ) external;

    // Views
    function isNonceUsed(uint64 srcChainId, uint256 nonce)
        external view returns (bool);
    function backingRatio(address token)
        external view returns (uint256);
}
\end{lstlisting}

\subsection{State Variables}

The contract holds five categories of state:

\begin{enumerate}[nosep]
  \item \textbf{MPC public key} --- set once at deployment, rotated via 7-day timelock.
  \item \textbf{Nonce bitmaps} --- \texttt{mapping(uint64 => mapping(uint256 => bool))}, one per source chain.
  \item \textbf{Release counters} --- \texttt{mapping(uint64 => uint256)}, enforcing Property~\ref{prop:seq-nonce}.
  \item \textbf{Backing state} --- per-token latest backing amount, timestamp, and derived pause flag.
  \item \textbf{Yield state} --- per-token share price numerator and epoch index.
\end{enumerate}

The contract is non-upgradeable. No proxy pattern, no \texttt{delegatecall}, no admin functions beyond timelocked MPC key rotation.

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