CCC ETH Lock

CCC (Common Chains Connector) is a framework that enables interoperability between wallets from different blockchain ecosystems and Nervos CKB. It leverages CKB’s flexibility in cryptographic verification to validate signatures from external chains like BTC and ETH.

CCC ETH Lock uses Ethereum addresses as the lock arguments, which are derived from secp256k1 public keys. It allows transactions on CKB to be signed and authorized using Ethereum-compatible wallets.

How It Works

Detailed Overview

Detailed documentation

Lock Script Structure

The Lock Script has the following properties:

• code_hash: The code hash of the deployed CCC Ethereum lock script

• hash_type: Typically "type"

• args: A 20-byte secp256k1 public key hash (Ethereum address), calculated as:

  1. Apply Keccak hash on the uncompressed secp256k1 public key (64 bytes).
  2. Take the last 20 bytes of the result. This is referred to as keccak160.

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Signature Format

The lock field in WitnessArgs must contain a 65-byte secp256k1 signature:

<r (32 bytes)> <s (32 bytes)> <v (1 byte)>

• The v value must be either 27 or 28. Any other value is rejected.
• The recovery ID (recId) is computed as v - 27.

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Unlocking Process

To validate the signature:

1. Add a byte representing the length of the prefix string (25).
2. Add the 25-byte string "Ethereum Signed Message:\n".
3. Add the message length as a 3-byte decimal string (e.g., "155").
4. Add the actual message body:

Signing a CKB transaction: 0x{sighash_all}

IMPORTANT: Please verify the integrity and authenticity of connected Ethereum wallet before signing this message

{sighash_all} is a 32-byte digest (in hex format) calculated using ckbhash (a blake2b variant).

This complete message is hashed with Keccak. The resulting hash is used for secp256k1 signature verification. The signature and recId are used to recover the uncompressed public key. Then keccak160 is applied to the recovered key and compared to the script args. If they match, the Script validates successfully.

Deployment

• Testnet

parameter	value
code_hash	0x5b1983cf4242009f72e82b37fb6b36790e6d4858474046fc3c798e5142cf8835
hash_type	type
tx_hash	0x2e6a50a9ce96c7b9697ed0fd21bd0a736d3df5e62d25137f728d8354a36cb369
index	0x0
dep_type	code