Statechains are an original second layer protocol originally developed by Ruben Somsen in 2018, depending on the eltoo (or LN Symmetry) proposal. In 2021 a variation of the original proposal, Mercury, was built by CommerceBlock. In 2024, a further iteration of the original Mercury scheme was built, Mercury Layer. 

The Statechain protocol is a bit more complicated to discuss compared to other systems such as Ark or Lightning because of the range of variations that are possible between the original proposed design, the two that have been actually implemented, and other possible designs that have been loosely proposed. 

Like Ark, Statechains depend on a centralized coordinating…

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