# Transaction signing overview

Transaction signing lets users cryptographically approve a specific action—such as a payment or money transfer—by authenticating with a registered credential. The signature binds the user's approval to the exact transaction details (the approval data), producing verifiable proof of consent that Mosaic embeds in the issued tokens.

Mosaic supports transaction signing with several authenticators, implemented as [journey](/guides/journeys_intro) steps. Using journeys implies integrating the Orchestration SDK to run the flow and the Authentication SDK to sign the transaction on the device. The table below maps each capability to its journey step guide.

div
| Signing method | Journey step |
|  --- | --- |
| Passkeys (WebAuthn) | [Guide](/guides/orchestration/journeys/transaction_signing_webauthn) |
| Mobile biometrics | [Guide](/guides/orchestration/journeys/transaction_signing_mobile_biometrics) |
| Mobile PIN | [Guide](/guides/orchestration/journeys/transaction_signing_mobile_pin) |
| TOTP | [Guide](/guides/orchestration/journeys/transaction_signing_totp) |
| Push notifications (web to mobile) | [Guide](/guides/orchestration/journeys/transaction_signing_mobile_approve) |


In some cases, a standalone path using only the Authentication SDK is also available. For example, see the WebAuthn payment approval guides for [Android](/guides/webauthn/payment_approval_android) and [iOS](/guides/webauthn/payment_approval_ios).

For information about retaining and independently verifying transaction approvals, see [Offline transaction signing verification](/guides/user/transaction_signing_offline_verification).