---
title: Nonce process flow
description: When a customer has implemented the digested token Single Sign-on and wishes to add the security of a nonce, they follow a certain process flow.
locale: en-US
canonical_url: https://www.servicenow.com/docs/r/australia/platform-security/authentication/c\_HighLevelOverview.html
release: australia
product: Authentication
classification: authentication
topic_type: concept
last_updated: "2026-03-12"
reading_time_minutes: 1
breadcrumb: [Implement a nonce, Local authentication, Authentication, Access Management]
---

# Nonce process flow

When a customer has implemented the digested token Single Sign-on and wishes to add the security of a nonce, they follow a certain process flow.

1.  A user logs into the customer's portal.
2.  The customer generates the required SSO parameters and appends a random nonce to the end. For example, if the customer were forwarding the authentication response via the query string, it may look something like this:

    ```
    SM_USER=itil&DE_USER=V1QuWMmxSfBgfRS099X0cAjKo5Q=&NONCE=1407743018
    ```


The instance receives this request and retrieves the authentication variables. Before attempting to verify the integrity of the authentication response, the instance checks the nonce against an internal table \(u\_authentication\_nonce\) to verify that it does not yet exist. If the nonce does not exist within that table, the nonce is then added to the table and the authentication process is allowed to continue. However, if that nonce value already exists within the table, the authentication attempt is cancelled and an error code of `failed_missing_requirement` is returned, which typically takes the user back to the login page.