Utility Functions

Table of Contents:

• Generate account alias
• Deserialize contract state
• Deserialize a receive function's return value
• Deserialize a function's error
• Deserialize a transaction
• Creating an AccountSigner
• Sign an account transaction
• Sign a message
• Deserialize smart contract types with only the specific type's schema
• Check smart contract for support for standards

The following shows how to generate an account alias. The alias is an alternative address, which is connected to the same account. The getAlias function takes a counter (0 <= counter < 2^24) to determine which alias to return.

const accountAddress = AccountAddress.fromBase58('3sAHwfehRNEnXk28W7A3XB3GzyBiuQkXLNRmDwDGPUe8JsoAcU');
const seperateAccount = AccountAddress.fromBase58('4ZJBYQbVp3zVZyjCXfZAAYBVkJMyVj8UKUNj9ox5YqTCBdBq2M');

const aliasCounter = 0;
const alias: AccountAddress.Type = AccountAddress.getAlias(accountAddress, aliasCounter);

console.log('Original address:', accountAddress.address);
console.log('Alias address:', alias.address);

// The function `isAlias` can be used to check if two acounts are aliases
if (!AccountAddress.isAlias(alias, accountAddress)) {
    throw Error('Expected accounts to be aliases!');
}

// Of course, using `isAlias` on a completely seperate account returns false
if (AccountAddress.isAlias(accountAddress, seperateAccount)) {
    throw Error('Two seperate accounts are claimed to be aliases!');
}

The following example demonstrates how to deserialize a contract's state:

    const contractName = "my-contract-name"
    const schema = Buffer.from(schemaSource); // Load schema from file
    const rawContractState = Buffer.from(stateSource); // Could be getinstanceInfo(...).model
    const state = deserializeContractState(contractName, schema, rawContractState);

The following example demonstrates how to deserialize a receive function's return value:

    const rawReturnValue = Buffer.from(returnValueSource);
    const schema = Buffer.from(schemaSource); // Load schema from file
    const contractName = "my-contract-name";
    const functionName = "receive-function";
    const schemaVersion = SchemaVersion.V1;
    const returnValue = deserializeReceiveReturnValue(
        rawReturnValue,
        schema,
        contractName,
        functionName,
        schemaVersion
    );

Note that for V0 contracts the schemaVersion should be SchemaVersion.V0. For V1 contracts it should currently be SchemaVersion.V1, unless the contract have been built using cargo-concordium >=2.0.0, which are internally versioned, and then the version does not need to be provided.

The following example demonstrates how to deserialize a receive function's error:

    const rawError = Buffer.from(errorSource);
    const schema = Buffer.from(schemaSource); // Load schema from file
    const contractName = "my-contract-name";
    const functionName = "receive-function";
    const error = deserializeReceiveError(rawError, schema, contractName, functionName);

Likewise for an init function's error:

    const rawError = Buffer.from(errorSource);
    const schema = Buffer.from(schemaSource); // Load schema from file
    const contractName = "my-contract-name";
    const error = deserializeInitError(rawError, schema, contractName);

The following example demonstrates how to deserialize a transaction:

const serializedTransaction: Buffer = ...
const deserialized = deserializeTransaction(serializedTransaction);
if (deserialized.kind === BlockItemKind.AccountTransactionKind) {
        // transaction is an account transaction
    const accountTransaction: AccountTransaction = deserialized.transaction.accountTransaction;
    const signatures: AccountTransactionSignature = deserialized.transaction.signatures;
    ...
    if (accountTransaction.type === AccountTransactionType.Transfer) {
        // transaction is a simple transfer
    }
} else if (deserialized.kind === BlockItemKind.CredentialDeploymentKind) {
    // transaction is a credentialDeployment
    const credentialDeployment = deserialized.transaction.credential;
}

Note that currently the only supported account transaction kinds are Transfer, TransferWithMemo and RegisterData. If attempting to deserialize other transaction kinds, the function will throw an error;

It is possible to build an AccountSigner in a variety of ways by utilizing the function buildAccountSigner.

If you have a wallet file export from a Concordium wallet it can be used:

const walletFile = fs.readFileSync(path.resolve(process.cwd(), cli.flags.walletFile), 'utf8');
const wallet = parseWallet(walletFile);

try {
    const signer = buildAccountSigner(wallet);

    signMessage(AccountAddress.fromBase58(wallet.value.address), 'test', signer).then(console.log);
} catch {
    console.error('File passed does not conform to a supported JSON format');
}

For a simple account, with a single credential and one keypair in the credential, one can also supply a single private key, like so:

    const privateKey = '...'; // Private key of an account as hex string
    const signer: AccountSigner = buildAccountSigner(privateKey);

For a more complex account with one or more credentials, each with one or more keypairs, buildAccountSigner is also compatible with the format created by the chain genesis tool, Concordium wallet exports, along with a map of type SimpleAccountKeys.

    const keys: SimpleAccountKeys = {
        0: {
            0: '...', // Private key of an account as hex string
            1: '...',
            ...
        },
        ...
    };
    const signer: AccountSigner = buildAccountSigner(keys);

The following example demonstrates how to use the signTransaction helper function to sign a account transaction:

    const accountTransaction: AccountTransaction = {
        header: header,
        payload: simpleTransfer,
        type: AccountTransactionType.Transfer,
    };

    // Sign transaction
    const signer = buildAccountSigner(walletExport);
    const signature: AccountTransactionSignature = await signTransaction(accountTransaction, signer);

    const transactionHash = await client.sendAccountTransaction(accountTransaction, signature);

The following is an example of how to sign an account transaction without using the signTransaction helper function:

    import * as ed from "@noble/ed25519";

    let accountTransaction: AccountTransaction;
    // Create the transaction
    // ...

    // Sign the transaction, the following is just an example, and any method for signing
    // with the key can be employed.
    const signingKey = "ce432f6bba0d47caec1f45739331dc354b6d749fdb8ab7c2b7f6cb24db39ca0c";
    const hashToSign = getAccountTransactionSignDigest(accountTransaction);
    const signature = Buffer.from(await ed.sign(hashToSign, signingKey)).toString("hex");

    // The signatures used to sign the transaction must be provided in a structured way,
    // so that each signature can be mapped to the credential that signed the transaction.
    // In this example we assume the key used was from the credential with index 0, and it
    // was the key with index 0.
    const signatures: AccountTransactionSignature = {
        0: {
            0: signature
        }
    };

To have an account sign an arbritrary message, one can use the signMessage function:

    const account = new AccountAddress("4ZJBYQbVp3zVZyjCXfZAAYBVkJMyVj8UKUNj9ox5YqTCBdBq2M");
    const message = "testMessage";
    const signer: AccountSigner = ...;
    const signature = signMessage(account, message, signer);

What is actually signed is the sha256 hash of the account address, eight zero bytes and the actual message. This ensures that the message cannot be an account transaction. To easily verify the signature, one can use the verifyMessageSignature function:

    const message = "testMessage";
    const signature = ...; // signature from signMessage
    const accountInfo = ...; // the getAccountInfo node entrypoint can be used for this
    if (!verifyMessageSignature(message, signature, accountInfo)) {
       // the signature is incorrect
    }

The message can either be a utf8 encoded string or a Uint8Array directly containing the message bytes.

The SDK exposes a general function to deserialize smart contract values from binary format to their JSON representation. In the previous sections the schema used was assumed to be the schema for an entire module, this function can be used with the schema containing only the specific type of the parameter, return value, event or error.

    const deserializedValue = deserializeTypeValue(serializedValue, rawTypeSchema);

Note that the specific schema can be obtained using cargo-concordium's schema-json command, and specifically for parameters, this SDK exposes functions for that, check the "serialize parameters with only the specific types schema" section on the transactions page for those.

To check if a smart contract supports a certain standard (according to CIS-0 standard detection), the utility function cis0Supports can be used. It should be noted, that the support of the contract is purely based on the claims of the contract and does not give any guarantees for whether the contract adheres to the standard it claims to implement. The function returns undefined if the contract does not support CIS-0.

This requires a ConcordiumGRPCClient.

    const client = ...; // `ConcordiumGRPCClient`
    const address = {index: 1234n, subindex: 0n}; // Contract to check for support.
    const standardId = 'CIS-2';
    // const standardIds = ['CIS-1', 'CIS-2']; // Example of a list of standards to check for.

    const supportResult = await cis0Supports(client, address, 'CIS-2');