Spacechain

A spacechain is a proposed type of Bitcoin sidechain that borrows Bitcoin's proof-of-work security through blind merged mining, without a federation, a custodial peg, or any new trusted party. The concept, developed by Ruben Somsen, aims to let an independent chain exist alongside Bitcoin while inheriting its security and requiring only a minimal (or no) consensus change.

Blind merged mining

In ordinary merged mining, a Bitcoin miner also runs the secondary chain's node and builds its blocks. Blind merged mining removes that requirement: a separate party constructs the spacechain block and pays a Bitcoin fee to have a commitment to it embedded in a Bitcoin transaction. The Bitcoin miner simply includes that transaction for the fee, "blindly" anchoring the spacechain block without running its software or doing any extra work. Whoever pays the most to commit the next block wins the right to extend the spacechain, turning Bitcoin's fee market into the spacechain's leader-election mechanism.

The hard part: the peg

Anchoring blocks is the easy half; moving bitcoin onto and off a spacechain trustlessly is the open problem. Proposals lean on covenant-like tools — notably AnyPrevOut and constructions such as a "succinct" or covenant-based two-way peg — to avoid a federation holding the funds. Until Bitcoin gains the needed primitives, fully trustless spacechain pegs remain experimental.

Spacechains are one point in the design space of Bitcoin layers and sidechains, alongside drivechains and merged mining. D-Central presents this as an educational reference to an active research idea, not active consensus.