xu {
    hscale = "1.2";

    CB [label=" ", linecolor="transparent"],
    N [label="Network", linecolor="#008800", textbgcolor="#CCFFCC", arclinecolor="#008800"],
    O [label="Offerer", linecolor="#FF0000", textbgcolor="#FFCCCC", arclinecolor="#FF0000"],
    B [label="Bidder", linecolor="#0000FF", textbgcolor="#CCCCFF", arclinecolor="#0000FF"],
    C [label=" ", linecolor="transparent"], C2 [label=" ", linecolor="transparent"];
    O =>> N [label="Sends Offer"];
    N >> B [label="Detects Offer"];
    B =>> O [label="Sends Bid"];
    B abox B [label="Bid Sent"];
    O box O [label="User accepts bid"];
    O =>> N [label="Sends Initiate Tx"],
    C note C2
        [label="Offerer generates secret_value and sends Hash(secret_value) to the Bidder",
         textbgcolor="#FFFFCC"];
    O =>> B [label="Sends BidAccept"],
    C note C2
        [label="ITX can be spent by
                knowledge of the secret_value and the bidder_redeem_key or
                after a timeout by the offerer_refund_key",
         textbgcolor="#FFFFCC"];

    B abox B [label="Bid Accepted"];
    N >> B [label="Detects Initiate Tx"];
    B abox B [label="ITX Sent", textbgcolor="#4bdbf1"];
    B => B [label="Wait for ITX to confirm"], O => O [label="Wait for ITX to confirm"];
    B abox B [label="ITX Confirmed", textbgcolor="#4bdbf1"];
    B =>> N [label="Sends Participate Tx"],
    C note C2
        [label="PTX can be spent by
                knowledge of the secret_value and the offerer_redeem_key or
                after a timeout by the bidder_refund_key",
         textbgcolor="#FFFFCC"];
    B abox B [label="PTX Sent", textbgcolor="#f1db4b"];
    N >> O [label="Detects Participate Tx"];
    B => B [label="Wait for PTX to confirm"], O => O [label="Wait for PTX to confirm"];
    B abox B [label="PTX Confirmed", textbgcolor="#f1db4b"];
    B abox B [label="Bid Participating"];
    O =>> N [label="Sends Participate Redeem Tx"],
    C note C2
        [label="Reveals secret_value",
         textbgcolor="#FFFFCC"];
    CB alt C [label="success path"] {
        N >> B [label="Detects Participate Redeem Tx"];
        B abox B [label="PTX Redeemed", textbgcolor="#f1db4b"];
        B =>> N [label="Sends Initiate Redeem Tx"];
        B => B [label="Wait for ITX Redeem to confirm"];
        B abox B [label="ITX Redeemed", textbgcolor="#4bdbf1"];
        B abox B [label="Bid Completed"];
    --- [label="fail path"];
        B => B [label="Wait for PTX locktime to expire"];
        B =>> N [label="PTX Refund Tx"];
        B => B [label="Wait for PTX Refund to confirm"];
        B abox B [label="PTX Refunded", textbgcolor="#f1db4b"];
    };
}