How device-backed login works
The most robust login pattern combines something you know (account credential) with something you have (the Trezor device). A typical challenge-response flow starts when the host (browser or server) sends a randomly generated challenge to the device via a secure connector (WebUSB, WebHID, or native integration). The Trezor signs that challenge inside the device using a key derived from your seed. Because the private key never leaves the device, the host can verify the signature without ever seeing the private key. This proves possession and allows the server to issue a short-lived session token.
Short-lived tokens reduce exposure: even if a token is intercepted, its limited lifetime and revocation mechanisms make replay attacks less practical. For highly sensitive operations — such as transferring funds — require device re-confirmation rather than relying solely on session tokens. This layered approach combines usability with strong cryptographic guarantees.