CIP30 API

CIP30 (Cardano Improvement Proposal 30) defines a standard for dApp-wallet communication on the Cardano blockchain. The Cardano Client Library provides CIP30-compatible data signing and verification built on CIP8 COSE Sign1. It bundles the signing flow—header construction, Sig_Structure generation, signing, and verification—into a small surface so you can focus on wallet UX instead of COSE internals.

Key Features

Data Signing: CIP30DataSigner.signData(...)
Verification: CIP30DataSigner.verify(DataSignature)
COSE Integration: Uses CIP8 builders internally
UTXO Bridge: CIP30UtxoSupplier for hex-encoded UTxOs

Dependencies

Group ID: com.bloxbean.cardano
Artifact ID: cardano-client-cip30
Dependencies: cip8, core

Usage Examples

Signing Data with CIP30

Sign arbitrary payload bytes together with the user’s address (embedded in COSE headers) to prove address ownership.


// Create account for signing
Account signerAccount = Account.createFromMnemonic(Networks.testnet(), "your mnemonic words");
 
byte[] addressBytes = signerAccount.baseAddress().getBytes();
byte[] payload = "Hello from dApp!".getBytes(StandardCharsets.UTF_8);
 
DataSignature dataSignature = CIP30DataSigner.INSTANCE.signData(
        addressBytes,
        payload,
        signerAccount);
 
String signatureHex = dataSignature.signature();
String keyHex = dataSignature.key();

Verifying CIP30 Signatures

Verify both the signature and that the address in the protected header matches the public key used for signing.


DataSignature dataSignature = new DataSignature(signatureHex, keyHex);
 
boolean isValid = CIP30DataSigner.INSTANCE.verify(dataSignature);

Working with DataSignature Objects

Read back address, curve, and public key information from the COSE-encoded signature without manual parsing.


DataSignature dataSignature = new DataSignature(signatureHex, keyHex);
 
byte[] addressFromSignature = dataSignature.address();
Integer crv = dataSignature.crv();
byte[] x = dataSignature.x();

Signing with Hash Payload

Enable hashing for large payloads so only a Blake2b-224 hash is signed instead of the full data.


DataSignature dataSignature = CIP30DataSigner.INSTANCE.signData(
        addressBytes,
        largePayload,
        signerAccount,
        true // hashPayload = true
);

UTXO Management (CIP30UtxoSupplier)

Convert wallet-provided hex-encoded CBOR UTxOs into the library’s UtxoSupplier for transaction building.


// Hex-encoded CBOR UTxOs from wallet getUtxos()
List<String> walletUtxos = fetchFromWallet();
 
CIP30UtxoSupplier utxoSupplier = new CIP30UtxoSupplier(walletUtxos);
List<Utxo> page = utxoSupplier.getPage(address, 20, 0, OrderEnum.asc);

API Reference

CIP30DataSigner


// Sign data
public DataSignature signData(@NonNull byte[] addressBytes, @NonNull byte[] payload, @NonNull Account signer)
public DataSignature signData(@NonNull byte[] addressBytes, @NonNull byte[] payload, @NonNull Account signer, boolean hashPayload)
public DataSignature signData(@NonNull byte[] addressBytes, @NonNull byte[] payload, @NonNull byte[] pvtKey, @NonNull byte[] pubKey)
public DataSignature signData(@NonNull byte[] addressBytes, @NonNull byte[] payload, @NonNull byte[] pvtKey, @NonNull byte[] pubKey, boolean hashPayload)
 
// Verify signature
public boolean verify(@NonNull DataSignature dataSignature)

DataSignature


public DataSignature(@NonNull String signature, @NonNull String key)
 
public DataSignature signature(@NonNull String signature)
public DataSignature key(@NonNull String key)
 
public byte[] address() // address bytes from protected header
public Integer crv() // curve id from COSE_Key other header
public byte[] x() // public key bytes (x) from COSE_Key other header

CIP30UtxoSupplier


// Construct from hex-encoded CBOR UTxOs
public CIP30UtxoSupplier(List<String> hexEncodedCborUtxos)
 
public List<Utxo> getPage(String address, Integer pageSize, Integer page, OrderEnum order)
public Optional<Utxo> getTxOutput(String txHash, int outputIndex)
public List<Utxo> getAll(String paymentAddress)

Constants (`CIP30Constant`)

ADDRESS_KEY: “address” (stored in protected header other map)
ALG_EdDSA: -8
CRV_Ed25519: 6
OKP: 1
X_KEY: -2 (public key bytes)
CRV_KEY: -1 (curve id)

CIP30 Data Signing Flow

CIP30DataSigner builds a CIP8 COSE_Sign1 with the payload (optionally hashed) and address in headers.
Signature is created with Configuration.INSTANCE.getSigningProvider().
DataSignature stores the hex-encoded COSE_Sign1 and COSE_Key.
verify recreates the SigStructure, checks the signature, and verifies the address against the key.

Integration with Other Standards

CIP8: All signing uses the CIP8 COSE builders.
CIP67/68/25: Use normal transaction-building APIs for assets/metadata; CIP30 only covers data signing.

For more information about CIP30, refer to the official CIP30 specification .