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Nostr Binding Type Script Specification

Introduction

The Nostr binding type script enables the binding between a Nostr Note and a CKB cell.

ckbhash

CKB uses blake2b as the default hash algorithm. We use ckbhash to denote the blake2b hash function with following configuration:

output digest size: 32 personalization: ckb-default-hash

Type ID

Type ID is a mechanic widely used in CKB. Upon creation, it follows this rule:

Create a transaction which uses any out point as tx.inputs[0] and has a output cell whose type script is Type ID. The output cell's type script args is the hash of tx.inputs[0] and its output index. Because any out point can only be used once as an input, tx.inputs[0] and thus the new type id must be different in each creation transaction.

The hash of tx.inputs[0] and its output index via ckbhash can be referred to as the global unique ID.

Script

A nostr binding type script has the following structure:

Code hash: nostr binding type script code hash
Hash type: nostr binding type script hash type
Args: <nostr event id for binding, 32 bytes> <global unique ID, 32 bytes>

The global unique ID follows rules defined in Type ID RFC.

Witness

Hexadecimal strings are frequently used in event in JSON format. Only lowercase letters can be used in hexadecimal strings. For example, "00" and "ffee" are valid hexadecimal strings, while "FFEE" and "hello world" are not valid. This convention is applied throughout this specification.

When there is the same type script in input cells(transfer, burn), the witness is ignored.

When there is no same type script in input cells(mint), the corresponding witness must be a proper WitnessArgs data structure in molecule format. In output_type field of the WitnessArgs, an event from NIP-01 structure must be present in JSON format encoded in UTF-8. The id of event should be verified according to NIP-01 and be equal to nostr event id for binding on script args. In this event, there must be a tag key with name "ckb_global_unique_id" and its corresponding tag value is equal to global unique ID on script args in hexadecimal string. Finally, the sig field, along with the pubkey and id fields in the event, can be validated via Schnorr verification.

Examples

Mint

CellDeps:
    <vec> Nostr binding type script cell
Inputs:
    <vec> normal cell (consumed to generated global unique ID)
Outputs:
    <vec> Nostr binding cell
        Data: <...>
        Lock: <...>
        Type:
            code_hash: <nostr binding type script code hash>
            args: <event id, 0011...eeff><global unique ID, aabb...0011>
Witnesses:
    <vec> WitnessArgs
        lock: <...>
        input_type: <...>
        output_type: >
            {
                "id": "0011...eeff",
                "pubkey": <schnorr pubkey, "dead...beef">,
                "created_at": <unix timestamp in seconds>,
                "kind": <0~65535>,
                "tags": [
                    ["ckb_global_unique_id", "aabb...0011"]
                ],
                "content": <arbitrary string>,
                "sig": <schnorr signature, "ffee...0000">
            }

Transfer

CellDeps:
    <vec> Nostr binding type script cell
Inputs:
    <vec> Nostr binding cell
        Data: <...>
        Lock: <...>
        Type:
            code_hash: <nostr binding type script code hash>
            args: <event id, 0011...eeff><global unique ID, aabb...0011>
Outputs:
    <vec> Nostr binding cell
        Data: <...>
        Lock: <...>
        Type:
            code_hash: <nostr binding type script code hash>
            args: <event id, 0011...eeff><global unique ID, aabb...0011>
Witnesses:
    <...>

Burn

CellDeps:
    <vec> Nostr binding type script cell
Inputs:
    <vec> Nostr binding cell
        Data: <...>
        Lock: <...>
        Type:
            code_hash: <nostr binding type script code hash>
            args: <event id, 0011...eeff><global unique ID, aabb...0011>
Outputs:
    <vec> Other cells
Witnesses:
    <...>

Notes

An implementation of the nostr lock script spec above has been deployed to CKB mainnet and testnet:

  • mainnet
parameter value
code_hash 0xb56ea08c4b10b454ed3389bb0e504ecfc57dcfe3089a5030654525a2def2108e
hash_type type
tx_hash 0xa3a63292ce23600faa508f2b2762d1a41d520eb4dd582a2dc544424ce06c3870
index 0x0
dep_type code
  • testnet
parameter value
code_hash 0x4105801324b70b3a1508ded8958aba66a6faf68cab26f863b4902b50dfb8b9ab
hash_type type
tx_hash 0x0e3949fa8afbbdf6d4abdda0d12ac1206c8d05dd51ec490b7341586291db85a6
index 0x0
dep_type code

Reproducible build is supported to verify the deploy script. To build the deployed the script above, one can use the following steps:

git clone https://github.com/cryptape/nostr-binding.git
cd nostr-binding
git checkout ec480b0
bash scripts/reproducible_build_docker