Gnosis Safe

Gnosis Safe: Multi-Sig Transactions

Gnosis Safe (now "Safe") is the most widely used multi-signature wallet on Ethereum. Nethereum's Nethereum.GnosisSafe package provides three levels of integration: SafeAccount (transparent — any contract service auto-routes through Safe), ChangeContractHandlerToSafeExecTransaction (per-service switching), and manual transaction building with EIP-712 signatures.

NuGet: Nethereum.GnosisSafe

dotnet add package Nethereum.GnosisSafe

SafeAccount (Recommended)

The simplest approach — create a SafeAccount and every contract service created from that web3 instance automatically executes through the Safe:

var safeAccount = new SafeAccount(safeAddress, chainId, privateKey);
var web3 = new Web3(safeAccount, rpcUrl);

// This ERC-20 transfer executes through the Safe
var erc20 = new ERC20ContractService(web3.Eth, tokenAddress);
var receipt = await erc20.TransferRequestAndWaitForReceiptAsync(to, amount);

SafeAccount implements IContractServiceConfigurableAccount, which swaps the contract handler to SafeExecTransactionContractHandler. The call data gets packed into a Safe execTransaction, signed with EIP-712, and submitted.

Per-Service Handler Swap

Switch a specific contract service to Safe execution without changing the entire web3:

var erc20 = new ERC20ContractService(web3.Eth, contractAddress);
erc20.ChangeContractHandlerToSafeExecTransaction(safeAddress, privateKey);
// Only this service goes through Safe; others execute directly

This is useful when some operations should go through the Safe and others shouldn't.

Manual Transaction Building

For full control or multi-owner signature collection:

var safeService = new GnosisSafeService(web3, safeAddress);

var transactionData = new EncodeTransactionDataFunction
{
    To = targetAddress,
    Value = 0,
    Data = encodedCallData,
    Operation = 0,  // 0 = Call, 1 = DelegateCall
    SafeTxGas = 0,
    BaseGas = 0,
    SafeGasPrice = 0,
    GasToken = AddressUtil.ZERO_ADDRESS,
    RefundReceiver = AddressUtil.ZERO_ADDRESS
};

var execTx = await safeService.BuildTransactionAsync(
    transactionData, chainId, false, privateKey1, privateKey2);

var receipt = await safeService.ExecTransactionRequestAndWaitForReceiptAsync(execTx);

BuildTransactionAsync fetches the nonce, hashes the data with EIP-712, signs with each key, orders signatures by signer address (required by Safe), and returns a ready-to-submit function.

Off-Chain Signature Collection

When owners can't sign in the same session, compute the hash and collect signatures separately:

// Compute hash
transactionData.SafeNonce = await safeService.NonceQueryAsync();
var safeHashes = GnosisSafeService.GetSafeHashes(transactionData, chainId, safeAddress);

// Each owner signs independently
var signature = await safeService.SignEncodedTransactionDataAsync(
    transactionData, chainId, convertToSafeVFormat: true);

Safe uses a custom V format (V+4 from standard Ethereum). The convertToSafeVFormat: true parameter handles this automatically.

Combine and Execute

var signatures = new List<SafeSignature>
{
    new SafeSignature { Address = owner1Address, Signature = signature1 },
    new SafeSignature { Address = owner2Address, Signature = signature2 }
};

var combinedSignatures = safeService.GetCombinedSignaturesInOrder(signatures);

Safe requires signatures ordered by signer address (ascending). GetCombinedSignaturesInOrder handles sorting and concatenation.

MultiSend

Batch multiple actions in a single Safe transaction using typed MultiSendFunctionInput<T>:

var input1 = new MultiSendFunctionInput<TransferFunction>(
    new TransferFunction { To = recipient1, Value = amount1 }, tokenAddress);

var input2 = new MultiSendFunctionInput<TransferFunction>(
    new TransferFunction { To = recipient2, Value = amount2 }, tokenAddress);

var execTx = await safeService.BuildMultiSendTransactionAsync(
    transactionData, chainId, privateKey, false, input1, input2);
var receipt = await safeService.ExecTransactionRequestAndWaitForReceiptAsync(execTx);

MultiSendFunctionInput<T> implements IMultiSendInput and encodes call data automatically. BuildMultiSendTransactionAsync sets Operation to DelegateCall (required by MultiSend).

Query Safe Configuration

var owners = await safeService.GetOwnersQueryAsync();
var threshold = await safeService.GetThresholdQueryAsync();
var nonce = await safeService.NonceQueryAsync();
var version = await safeService.VersionQueryAsync();
var isOwner = await safeService.IsOwnerQueryAsync(address);

Console.WriteLine($"Safe v{version}: {owners.Count} owners, threshold {threshold}, nonce {nonce}");

Gas Parameters

For most use cases, setting all gas parameters to 0 is correct — the Safe uses Ethereum's standard gas mechanism.

When to Use Which Approach

For full documentation, see: https://docs.nethereum.com/docs/defi/guide-gnosis-safe