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ProtocolsBitcoin Optech
Bitcoin Optech Newsletter #428
Bitcoin Optech 通讯第428期
Adam Gibson's Lichen design lets users exit a single-issuer layer 2 without the hub's cooperation, but the negotiated cap on the hub's own bitcoin limits how much inbound value they can actually redeem.
Judgment
A prospective Lichen user's decision changes: they can rely on the 2-of-2 exit for their own locked output, but tokens received from others are redeemable beyond the hub's negotiated bitcoin cap only at the hub's discretion, so the cap sets the real inbound redemption limit.
Basis
Adam Gibson posted a paper and proof-of-concept to Bitcoin-Dev for Lichen, a single-issuer layer 2 run by a sequencer. Each user holds a 2-of-2 contract with the hub and locks bitcoin in their own output, receiving equal tokens on the L2. To exit, the user returns tokens and collects from that output; the hub also locks its own bitcoin in each output up to a negotiated cap, like LN inbound liquidity, so the user can redeem tokens received from others. Tokens beyond the cap are redeemable only at hub discretion. If the hub refuses or is offline, the user generates a Groth16 proof that the sequencer signed a state recording returned tokens; because Script cannot verify it, the user claims a fixed verifier accepts it, and disputed cases use presigned BitVMX transactions to narrow to one execution step Script can check. Each side locks a reserve forfeited by losing a dispute.
Unclear The source does not say how the negotiated cap is set, how often it can change, or whether users can verify the hub's bitcoin reserve before accepting tokens.
Next Check Gibson's paper or Bitcoin-Dev follow-ups for an explicit method to set and verify the per-user cap before treating it as a user-side risk control.