papers/lux-ats-architecture/sections/06-settlement.tex

\section{Settlement}
\label{sec:settlement}

\subsection{Atomic T+0 Settlement}

Settlement occurs atomically on Lux EVM. A settlement transaction bundles the securities transfer and the payment transfer into a single atomic operation:

\begin{lstlisting}[language=Solidity,caption={Atomic settlement contract.}]
contract AtomicSettlement {
    function settle(
        address securityToken,
        address paymentToken,
        address seller,
        address buyer,
        uint256 securityAmount,
        uint256 paymentAmount,
        bytes calldata mpcSignature
    ) external {
        require(
            verifyMPCSignature(
                keccak256(abi.encodePacked(
                    securityToken, paymentToken,
                    seller, buyer,
                    securityAmount, paymentAmount
                )),
                mpcSignature
            ),
            "invalid MPC signature"
        );

        IERC1400(securityToken).transferByPartition(
            DEFAULT_PARTITION,
            seller,
            buyer,
            securityAmount,
            ""
        );

        IERC20(paymentToken).transferFrom(
            buyer, seller, paymentAmount
        );

        emit Settled(
            securityToken, seller, buyer,
            securityAmount, paymentAmount,
            block.timestamp
        );
    }
}
\end{lstlisting}

\subsection{Settlement Finality}

Lux consensus provides probabilistic finality within 1--2 seconds. For securities settlement, the ATS waits for deterministic finality (block confirmation) before updating the settlement status. The settlement timeline comparison:

\begin{table}[H]
\centering
\caption{Settlement time comparison.}
\label{tab:settlement}
\begin{tabular}{lll}
\toprule
\textbf{System} & \textbf{Settlement Time} & \textbf{Counterparty Risk} \\
\midrule
Traditional equities (DTCC) & T+1 & Full during settlement period \\
tZERO & T+0 (claimed) & Custodial during settlement \\
Securitize Markets & T+1 to T+3 & Custodial during settlement \\
INX & T+0 to T+2 & Custodial during settlement \\
\textbf{Lux ATS} & \textbf{T+0 atomic} & \textbf{None (non-custodial)} \\
\bottomrule
\end{tabular}
\end{table}