Multisig Digital Bearer Instruments: Trustless Digital Cash

We propose Multisig Digital Bearer Instruments (MBI) — a trustless cryptographic bearer instrument for Bitcoin in which the issuer is structurally incapable of post-issuance interference. The bearer holds the spending threshold of a 2-of-3 multisignature script; the issuer holds one sub-threshold key deleted before funding. Transfer is key handover requiring no on-chain transaction, no network connection, and no fee. A proof-of-concept on Bitcoin Signet confirms the core security properties on live hardware.