Simplicity Debuts as Bitcoin’s Answer to Ethereum’s Solidity

Blockstream, the developer of Bitcoin’s layer-2 protocol Liquid and led by Bitcoin cypherpunk Adam Back, has launched Simplicity, a new smart contract language designed for Bitcoin.

According to a Thursday announcement shared with Cointelegraph, Simplicity smart contracts will be integrated into Liquid. The company said the move marks a step forward in transforming Bitcoin (BTC) from a secure store of value into a programmable foundation for decentralized finance.

The company also introduced SimplicityHL, a higher-level implementation of the language that facilitates easier development with increased abstraction.

A Blockstream representative told Cointelegraph that this version of the language “is here and usable today,” with a web-based integrated development environment also available.

A different approach for a different architecture

Simplicity differs from Ethereum’s Solidity language, largely due to the different underlying architectures of the two blockchains.

Related: StarkWare researchers propose smart contracts for Bitcoin with ColliderVM

This stems from different approaches and different architectures of the Ethereum and Bitcoin networks, with Solidity developed for the Ethereum Virtual Machine. State is the network’s agreed-upon snapshot of all account balances and stored data at a given block.

Bitcoin utilizes the unspent transaction output (UTXO) architecture, whereas the Ethereum network employs a network-wide state. This difference manifests itself in how Simplicity smart contracts work, with a Blockstream representative saying that “not relying on the global state is a big shift.” “Every bit of state your contract needs has to travel with the transaction.”

Blockstream’s researchers said Solidity developers will need to break their habit of reading from globally accessible variables and instead provide all necessary information at every step. In such a system, two smart contracts cannot share state or reference the same variables; everything must be explicitly passed within transactions. Still, the firm’s representatives explained that this approach also has a positive impact:

“Even if something goes wrong, only your contract’s specific part of the transaction graph is affected. It’s a different mindset compared to the global state, but it ultimately leads to safer and more contained contracts by design.“

Developers also won’t be able to use recursion or unbounded loops, which Blockstream claims aren’t necessary for onchain logic.

Related: A deep dive into the five popular smart contract development platforms and their comparison

The rise of domain-specific smart contract programming languages

Simplicity joins a growing list of domain-specific smart contract programming languages.

Noir, a programming language released in 2022 for writing and verifying zero-knowledge proofs (ZK-proofs), was adopted in 2023 by the developers of the upcoming privacy-first Ethereum layer-2 Aztec.

Noir has become a smart contract programming language specifically built for privacy-preserving applications that integrate ZK-proofs deeply into their architecture.

Another example is Leo, a smart contract programming language that also creates ZK-proof systems with closely related syntax and privacy in mind.

Ethereum’s Vyper is an EVM-compatible language designed to reduce the attack surface, which is now used by some leading Ethereum decentralized finance (DeFi) protocols.

Magazine: ZK-proofs are bringing smart contracts to Bitcoin — BitcoinOS and Starknet