eBTC

eBTC (enchanted BTC) is Bitcoin wrapped as a charm.

eBTC tokens are minted by locking BTC in the eBTC vault (bc1qrn970793udj0ugc3pj0hyrptts4rw5n7qxeya2) and burned by spending BTC from it. The amount of eBTC minted or burned equals the BTC amount minus 300 sats (dust) per vault UTXO.

A CHIP-0420 reference NFT provides on-chain metadata for the token (ticker, name, description, etc.). See ref-nft.md for NFT minting instructions.

Building

Prerequisites

Install Wasm WASI P1 support:

rustup target add wasm32-wasip1

Build

cargo update
app_bin=$(charms app build)

The resulting Wasm binary will be at ./target/wasm32-wasip1/release/ebtc.wasm.

Get the verification key:

export app_vk=$(charms app vk $app_bin)

Minting eBTC

To mint eBTC tokens, create a transaction that sends BTC to the vault address and attaches the token and vault contract charms to the outputs.

# UTXO you're spending
export in_utxo_0="<txid>:<vout>"

# app_id: hash of the UTXO ID of the 1st input of the reference NFT minting transaction
export app_id="<app_id_hex>"

# vault output: BTC amount to lock (eBTC minted = amount - 300 dust)
export vault_amount=10000

# eBTC minted
export mint_amount=9700  # vault_amount - 300 (dust)

# change output
export change_dest=$(charms util dest --addr <your_change_address>)
export change_amount=<change_sats>

cat ./spells/mint-token.yaml | envsubst | charms spell check \
  --prev-txs=<prev_txs_hex> \
  --app-bins=${app_bin}

The spell in spells/mint-token.yaml creates:

• An output at the vault address carrying the vault contract charm (c)
• An output carrying the newly minted eBTC tokens (t)

The token contract verifies that the eBTC minted equals the BTC locked minus 300 sats dust per vault UTXO.

Burning eBTC

To burn eBTC, spend a vault UTXO (BTC leaves the vault) and destroy the corresponding amount of eBTC tokens. The amount burned equals the BTC spent from the vault minus 300 sats dust per vault input.