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# SSO with Ethereum and Next JS

Ditch password fatigue and centralized databases for decentralized digital passports. Learn how to build secure, gas-free single sign-on in Next.js using Ethereum wallets and off-chain cryptography.

- **Speakers:** Rahat Chowdhury
- **Event:** JavaScript Congress
- **Published:** November 24, 2021
- **Duration:** 44:49
- **URL:** https://www.wearedevelopers.com/videos/288-sso-with-ethereum-and-next-js

## Summary

Traditional authentication methods suffer from significant user experience and security drawbacks, ranging from password fatigue to the heavy reliance on centralized social login providers that introduce single points of failure. As an alternative, developers can leverage Web3 wallet infrastructure as a decentralized identity provider, offering a "single sign-on associated to your wallet's public address." Rather than storing sensitive credentials, applications can treat EVM wallets as digital passports where users authenticate by verifying control over a cryptographic keypair.

Implementing Ethereum-based authentication within a Next.js application involves using serverless API routes alongside the Ethers.js library. The core security model hinges on backend nonce generation—a server-issued number used only once—which is passed to the client. The frontend then prompts the user's wallet, such as MetaMask, to cryptographically sign this nonce using their private key. Crucially, because these signing operations are mathematically resolved off-chain, the authentication process guarantees high security without incurring any blockchain gas fees.

Once the frontend submits the signed message, the server decrypts the signature to verify it matches the user's expected public address. This architecture drastically reduces database liability; because the application solely stores publicly available wallet addresses instead of private credentials, a compromised database yields zero sensitive data. With tools like WalletConnect expanding compatibility to mobile wallets, decentralized authentication provides a smoother, highly secure login standard that inherently protects user privacy and removes centralized dependencies.

**Keywords:** ethereum single sign-on, web3 authentication protocols, next.js serverless application, evm wallet integration, ethers.js frontend implementation, cryptographic message signing, metamask browser extension, passwordless user authentication, backend nonce generation, decentralized identity management, walletconnect mobile integration, public key cryptography auth, database liability reduction, digital passport implementation

## Chapters

1. **Introduction to single sign-on with Ethereum** (00:00) — An overview of utilizing Ethereum wallets to authenticate users within Next.js applications.
1. **Analyzing friction in traditional authentication flows** (01:13) — Password fatigue, magic link context switches, and centralized social login failures disrupt standard user experiences.
1. **Understanding the mechanics of blockchain wallets** (03:30) — Wallets operate as public and private key pairs that grant access to decentralized blockchain networks.
1. **Leveraging cryptographic signatures for gasless authentication** (04:21) — Hashing user data with wallet signatures validates identities without incurring transaction fees on the network.
1. **Mapping the Web3 wallet connection process** (05:43) — Address checking, backend nonce generation, and front-end cryptographic hashing combine to enable single sign-on.
1. **Demonstrating blockchain data hashing through nonces** (08:46) — Modifying the generated nonce or corresponding data string immediately invalidates the assigned cryptographic hash sequence.
1. **Implementing frontend wallet connections with ethers.js** (10:01) — Injecting window objects and requesting provider access enables Next.js applications to retrieve active MetaMask accounts.
1. **Building serverless API routes for user verification** (14:28) — Backend endpoints generate random nonces for public addresses and validate the decoded signature against stored records.
1. **Executing a live Ethereum signature request demo** (18:52) — Signing a randomized message in MetaMask successfully authenticates the detected wallet address within the local servers.
1. **Adapting signature concepts to alternative blockchain ecosystems** (21:21) — Cryptographic payload signing principles translate successfully to other decentralized architectures like Solana and standalone passport models.
1. **Clarifying wallet storage and provider access rights** (23:34) — Public addresses serve as account references while sensitive storage remains strictly controlled by the chosen wallet provider.
1. **Evaluating ethers.js preferences and mobile wallet integration** (24:27) — Implementing WalletConnect infrastructure bypasses browser extension requirements by routing authentication workflows through native mobile applications.
1. **Supporting authentication for unestablished Ethereum users** (25:35) — Free application onboarding requires deploying compatible EVM wallets to leverage embedded background cryptographic verification systems.
1. **Expanding authentication compatibility across multiple wallet vendors** (27:23) — Forking the base implementation allows integration with comprehensive aggregation utilities to support broader decentralized software varieties.
1. **Utilizing preconfigured cryptographic algorithms within wallet architectures** (28:07) — Tapping into existing infrastructure bypasses extensive encryption setup by directly accessing hashing processes built into client software.
1. **Integrating biometric web authentication APIs with Web3** (29:06) — Extending native fingerprint recognition frameworks into decentralized web protocols remains an emerging space requiring dedicated standardization.
1. **Navigating account recovery and social verification models** (30:13) — Standard seed phrase exports currently manage access restoration as decentralized identity recovery transitions toward community-based verification protocols.
1. **Seeking managed authentication alternatives to Auth0 equivalents** (31:35) — Emerging decentralized domain utilities outline establishing standard single sign-on specifications to replicate legacy identity delivery networks.
1. **Connecting existing applications to non-Ethereum networks** (33:05) — Interfacing with standalone blockchains requires separate connection libraries since standard browser extensions strictly monitor EVM environments.
1. **Mitigating security concerns when maintaining public network addresses** (33:55) — Storing universally accessible blockchain identifiers eliminates severe liability concerns common in centralized database intrusion events.

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