taproot-script-demo

Description: Educational Taproot script-path spend demo in TypeScript. Implements tagged hashing, TapLeaf/TapBranch/TapTweak, internal→output key tweaking, control block construction, and a minimal script serializer for a OP_CHECKSIG tapleaf. Uses noble-curves for BIP340 Schnorr.

Not a full PSBT or tx builder; this focuses on the cryptographic plumbing of Taproot key- and script-paths. Educational only.

Features

• BIP340 tagged hash helper
• Taproot tapleaf hash (TapLeaf = sha256(tag="TapLeaf", ver||len||script))
• Merkle root for script tree (TapBranch)
• Key tweak: Q = P + H_tapTweak(P || merkle_root)·G
• Build control block for script-path spend
• Minimal script encoder and a single-leaf (xonly_pub) OP_CHECKSIG script
• Schnorr sign (BIP340) with tweaked key

Quickstart

npm i
npm run build
node dist/demo.js

Files

• src/taproot.ts — Taproot primitives (tagged hash, tweak, leaf, branch)
• src/script.ts — Minimal Bitcoin script serializer & helpers
• src/demo.ts — Builds a 1-leaf tree (OP_CHECKSIG) and prints tweaked pubkey & control block

Notes

• This does not build or sign full Bitcoin transactions or PSBTs.
• No bech32m encoding (address); we output the x-only pubkey for P2TR.
• Verified against the spec formulas; use a full library for production.