Bitcoin ZK client written in Cairo.
Shinigami is a zero-knowledge Bitcoin client implemented in Cairo. It aims to provide trustless validation of the Bitcoin blockchain through STARK proof verification. It is heavily inspired by ZeroSync project.
Disclaimer: This project is in the early stages of development and should not be used in production. It will evolve rapidly, expect breaking changes.
flowchart TB
Pnm1(STARK proof of the chain state up to the block <i>n - 1</i>, including utxo accumulator) --> Vp(zk verifier)
Bn(blocks <i>n..m</i>) ----> Vb
subgraph Cairo
Vp{{STARK verifier}}-->ChS(verified chain state)
ChS --> Vb{{validate block<br>against the chain state}}
Vb --> ChS
end
Vb --> Pn(STARK proof of the chain state up to the block <i>m</i>,<br> including utxo accumulator)
style Bn fill:pink
style Pn fill:lightgreen
style Pnm1 fill:lightgreen
style ChS fill:greenyellow
style Vp fill:gold
style Vb fill:gold
At its core, consensus client accepts two inputs: a batch of consecutive blocks n to m and a STARK proof of the state of the chain up to block n−1. It ensures that the historical chain state is valid by verifying the STARK proof. Then, it produces a new chain state by applying the new blocks on top of the historical state. As a result, a proof of the new state is generated.
Although this is a highly experimental project without immediate plans for deployment, there are many potential applications:
- light clients
- IBD speedup
- non custodial bridges
- layer 2s
Implement a reduced light client that can verify a range of blocks starting at genesis.
It does not have to validate execution, just check that the block header fields follow the protocol.
Tasks:
- block hash computation
- proof-of-work validation/computation
- block time validation/computation
- block difficulty adjustment
- script for fetching arbitrary block data
- script for preparing program arguments
- script for running the program e2e for multiple blocks
Extend light client with partial transaction validation, but without UTXO checks.
Tasks:
- reassess validation check list (analyze Bitcoin core codebase)
- generate & run integration tests e2e instead of Cairo codegen
- transaction ID calculation
- transaction root computation
- validate transaction fee
- validate coinbase transaction
- validate that transaction can be mined (locktime, sequence, coinbase maturity)
- validate segwit specific data (wtxid commitment)
- validate block weight
- script that fetches blocks extended with references UTXOs
- script that runs the program e2e for a span of blocks
Try to run script validation with external Cairo crate.
Tasks:
- Integrate Shinigami-script
Add inclusion proofs for the UTXOs included in the block.
Tasks:
- isolate unspendable outputs (OP_RETURN, etc)
- implement cache for UTXOs spent in the same block they are created (*)
- implement transaction outpoint hashing
- implement Utreexo accumulator (addition)
- Utreexo backend that maintains utxo set and Utreexo roots
- implement Utreexo single inclusion proof verification
- implement Utreexo single output removal
- implement Utreexo bridge node that generates individual inclusion proofs
- implement script that runs the program e2e for a span of blocks
Validate full block execution, including the Bitcoin scripts checks and Utreexo.
- identify Cairo code botlenecks
- consider using garaga msm to batch signature verifications
Recursively verify STARK proofs of chain state updates. Still largely tbd.
- use garaga to implement signature verifications
This will compile all the packages:
scarb buildThis will run tests for all the packages:
scarb testInstall necessary packages required by Python scripts:
pip install -r scripts/data/requirements.txtThanks goes to these wonderful people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!