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Gnosis Pay authenticates users through Sign-In with Ethereum (SIWE) following EIP 4361 in which it verifies a cryptographic signature produced by the user’s wallet proving control of the address. Once that signature is verified, the API issues a pair of tokens (access and refresh) that represent the authenticated session going forward. This page explains the reasoning behind both pieces: why SIWE, and how the token system keeps a session secure without asking the user to sign a message on every request.

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Sign in with Ethereum

SIWE (formalized as EIP-4361) defines a standard, human-readable message format that a wallet signs to prove address ownership.
  • Signed message: The signed message itself states who is authenticating, for which domain, at what time, and often includes a random nonce. The user can visually inspect what they’re agreeing to before signing, rather than blindly approving an opaque hash.
  • Domain-bound: Because the message includes the requesting domain, a signature obtained on app.example.com can’t be silently replayed against Gnosis Pay’s own domain by a malicious site — this is what domain whitelisting on our side enforces.
  • Replay resistance: The nonce and timestamp in the message mean a captured signature can’t be reused indefinitely to mint new sessions.

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Session Management against Auth token

A signature proves identity for a single moment — it doesn’t create an ongoing session by itself. So once SIWE verification succeeds, Gnosis Pay issues two tokens that stand in for “this address is authenticated” over time:

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Why tokens rotate

Every time a refresh token is used, it’s invalidated and replaced with a new one this is token rotation. The old refresh token becomes permanently unusable the moment a new one is issued, even if it hasn’t expired yet. This turns refresh tokens into a kind of tripwire: in normal operation, only one “version” of a session’s refresh token is ever valid at a time. If a refresh token is ever used twice, once by the legitimate client, once by an attacker who copied it the system can detect that the token has already been consumed and end the session for everyone holding a copy.
For the actual request/response and endpoints to implement this flow, see the Authentication Guide.