How to generate the address of a plutus script using Cardano Serialization Lib?

Question

I am sending some smart contracts using the Cardano Serialization Lib and the nami wallet for signing, everything works fine, but I am not able to get the script address of a Plutus Script. I have managed it out using cardano-cli command 'address build'. But I think there most be some equivalent in Cardano Serialization Lib, is it posible? I tried with the method Address.from_bytes() using the hex-decoded CBOR from the plutus script but it says it is not the right kind of CBOR.

Answer 1

Here is a javascript snippet that uses the cardano-serialization-lib to go from CBORHex to addr_test...

const {
  ScriptHash,
  NetworkInfo,
  EnterpriseAddress,
  StakeCredential
} = require("@emurgo/cardano-serialization-lib-nodejs")

...

const addrFromHash = (hash) => {
  const scripthash = ScriptHash.from_bytes(Buffer.from(hash,"hex"));
  const cred = StakeCredential.from_scripthash(scripthash);
  const networkId = NetworkInfo.testnet().network_id();
  const baseAddr = EnterpriseAddress.new(networkId, cred);
  const addr = baseAddr.to_address();
  const addrBech32 = addr.to_bech32();
  return addrBech32;
}

Answer 2

Plutus-Core script bytes are wrapped twice in a CBOR bytearray.

Use the following steps to calculate the script address:

1. unwrap one layer of CBOR
2. prepend a byte representing the PlutusScript version: 0x01 for PlutusScriptV1, 0x02 for PlutusScriptV2
3. calculate the 28-byte (224-bit) blake2b digest to get the payment part of the address
4. form the full script address using CIP19 (so for script addresses without a staking part simply prepend 0x70 to the digest)
5. encode the script address bytes using bech32 ("addr_test" prefix for testnet, "addr" prefix for mainnet)

The pseudo code of these steps would look as follows:

encodeBech32("addr_test", prepend(hashBlake2b224(prepend(unwrapCborBytes(hexToBytes(cborHex)), 0x01)), 0x70))

As an example consider the commonly used AlwaysSucceeds script. It has the following hexadecimal representation: "4e4d01000033222220051200120011".

1. Unwrapping one layer of CBOR bytearray would give: "4d01000033222220051200120011".
2. Prepend 0x01: "014d01000033222220051200120011"
3. Blake2b 28-byte digest: "67f33146617a5e61936081db3b2117cbf59bd2123748f58ac9678656"
4. Prepend 0x70: "7067f33146617a5e61936081db3b2117cbf59bd2123748f58ac9678656"
5. Bech32 encoding of testnet address: "addr_test1wpnlxv2xv9a9ucvnvzqakwepzl9ltx7jzgm53av2e9ncv4sysemm8"

Don't ask me why Plutus-Core scripts are wrapped twice in CBOR, and then unwrapped once to calculate the address. Some smart guys somewhere must have a good reason.

If you'd like to do these calculations in Javascript without some complicated Rust/Haskell dependencies check out the Helios Lang library. The library is UNLICENSEd so you can copy the relevant functionality as you please.

Answer 3

Script addresses are basically just addresses that uses the key hash instead of payment key hash, see the CIP19: Cardano Addresses.

However, the cardano-serialization-lib does not support fee estimation for these, but Alessandro from Nami has a patch for that.