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Nethereum.Siwe

NuGet: Nethereum.Siwe | Source: src/Nethereum.Siwe/

Nethereum.Siwe

Full Sign-In with Ethereum (EIP-4361) implementation with session management, signature verification, and pluggable user validation. Built on top of Nethereum.Siwe.Core.

Key Components​

ClassPurpose
SiweMessageServiceOrchestrates the full SIWE flow: message building with nonce, signature verification, session matching, expiry checks
ISessionStorageInterface for storing SIWE sessions keyed by nonce
InMemorySessionNonceStorageDefault in-memory session store
IEthereumUserServicePluggable user validation (e.g. check NFT balance, database lookup)
ERC721BalanceEthereumUserServiceValidates users hold an ERC-721 token

Quick Start​

Server-side SIWE authentication​

// 1. Create the service (in-memory sessions, no user validation)
var siweService = new SiweMessageService();

// 2. Build a message for the user to sign
var message = new DefaultSiweMessage();
message.Address = userAddress.ConvertToEthereumChecksumAddress();
message.SetExpirationTime(DateTime.UtcNow.AddMinutes(10));
message.SetNotBefore(DateTime.UtcNow);
string messageToSign = siweService.BuildMessageToSign(message);
// Send messageToSign to the client for signing

// 3. Verify the signed message
var parsed = SiweMessageParser.Parse(messageToSign);
bool valid = await siweService.IsValidMessage(parsed, signature);

With NFT-gated access​

var userService = new ERC721BalanceEthereumUserService(web3, nftContractAddress);
var siweService = new SiweMessageService(
    new InMemorySessionNonceStorage(),
    userService);

// IsUserAddressRegistered checks the user holds the NFT
bool registered = await siweService.IsUserAddressRegistered(parsed);

Smart contract wallet support (ERC-1271 / ERC-6492)​

var siweService = new SiweMessageService(
    new InMemorySessionNonceStorage(),
    ethereumUserService: null,
    web3ForERC1271Validation: web3);

// IsMessageSignatureValid automatically falls back to ERC-1271/ERC-6492
// for smart contract wallets
bool valid = await siweService.IsMessageSignatureValid(parsed, signature);

Full Template​

A complete Blazor + REST API SIWE authentication template is available at Nethereum.Templates.Siwe, providing:

  • REST API — Nonce generation, authentication endpoint, JWT creation and middleware validation
  • Blazor WebAssembly — MetaMask signing, JWT local storage, SiweAuthenticationWasmStateProvider
  • Blazor Server — Direct signing via NethereumSiweAuthenticatorService, protected session storage
  • Blazor <AuthorizeView> — Role-based access with EthereumConnected and SiweAuthenticated claims

Relationship to Other Packages​

  • Nethereum.Siwe.Core — Message model, parser, and string builder
  • Nethereum.UI — NethereumSiweAuthenticatorService for Blazor Server SIWE flows
  • Nethereum.Signer — EthereumMessageSigner used for signature recovery
  • Nethereum.Contracts — ERC-1271 and ERC-6492 signature validation for smart contract wallets