In an announcement that rekindles the perennial debate over how far Bitcoin can—or should—stretch beyond its original remit, Input Output (IO), the research and engineering company behind Cardano, has unveiled a compilation pipeline that executes Cardano smart contracts on Bitcoin without touching a line of Bitcoin’s consensus code.
The thread describes a relay of representations that begins with high‑level source code and ends inside Bitcoin Script. First, Cardano’s tool‑chain lowers the contract into Untyped Plutus Core (UPLC), a stripped‑down functional bytecode. UPLC is then serialized and handed to a miniature interpreter known as the Control–Environment–Continuation (CEK) machine. Instead of asking Bitcoin to interpret UPLC directly, IO compiles the CEK machine itself into RISC‑V, “a real‑world, simple CPU instruction set.” The resulting RISC‑V program becomes the payload that Bitcoin ultimately verifies, with the serialized UPLC passed to it at run‑time.
A companion blog post signed by software engineer Riley Kilgore frames the design in a single sentence: “By combining a serialized smart contract format (Untyped Plutus Core – UPLC), a clever interpreter architecture (CEK machine), and a widely supported open‑source reduced instruction set architecture (RISC‑V), IO is turning that idea into reality.” Because the RISC‑V code is deterministic and its execution trace can be proven—or disputed—inside Bitcoin Script, no soft‑fork is required. Bitcoin remains unchanged; the expressiveness is off‑loaded to an auxiliary virtual CPU whose behaviour can be challenged step by step.
The promise is to bring Cardano’s eUTxO‑based smart‑contract ecosystem—Marlowe, Aiken, and the rest—into Bitcoin’s vast liquidity pool. In practical terms that could mean lending, swaps, and even NFT‑backed loans secured by BTC collateral, all without giving custodial control to a sidechain.
The compilation flow is still in active development; IO has not committed to a main‑net launch date, nor has it published gas‑cost benchmarks for typical contracts. What it has done is demonstrate a theoretically complete bridge between two philosophically divergent blockchains. If the engineering hurdles—transaction sizes, dispute latency, and user‑experience frictions—can be contained, Cardano’s software stack may soon become a first‑class citizen on Bitcoin.
At press time, ADA traded at $0.87.
