How does Kerberos preauthentication work?

Before a user receives a ticket from the Key Distribution Center (KDC), they must prove knowledge of the secret key, usually via an encrypted timestamp.

Which technologies can be used for preauthentication?

Preauthentication can involve Single Sign-On (SSO), Multi-Factor Authentication (MFA), Application Delivery Controller (ADC), firewalls, security gateways, Kerberos, Zero Trust architecture, and Identity and Access Management (IAM).

What are the benefits of preauthentication?

Stronger security, reduced risk of unauthorized access, and a seamless user experience.

How can Sicra help with preauthentication?

Sicra provides solutions at both application and network levels, as well as for Kerberos-based identity environments, combining security with usability.

Pre-authentication

What is pre-authentication?

Pre-authentication is a security mechanism that verifies identity before access is granted. The term is used in two main contexts:

Network and application security
Here, pre-authentication adds a layer in front of applications and services. This often involves a firewall, security gateway, or application delivery controller (ADC), and may include mechanisms such as multi-factor authentication, certificate validation, or IP checks.

The goal is to make this layer as invisible as possible for the user, by combining strong security with a seamless experience. This is often achieved through Single Sign-On (SSO), so users only notice extra security when truly needed.

Analogy: Like a guard at the door who checks your ID before you even get to see what’s inside – but without meeting multiple guards along the way.
Kerberos pre-authentication
In the Kerberos protocol, pre-authentication protects against offline password attacks. Before a user can obtain a ticket from the Key Distribution Center (KDC), they must prove they already know the secret key (derived from their password). This is done by sending a timestamp encrypted with the key.

Analogy: Like applying for a passport – you must present valid ID before the passport office even starts processing and issuing the passport.

Examples

A user tries to open a web application. Before the login screen appears, they pass through a pre-authentication layer provided by a security gateway. Thanks to SSO, the user doesn’t need to enter another password, as their identity is already confirmed.
A client sends a request to the Kerberos KDC. Before the KDC issues a ticket, the client must send an encrypted timestamp that proves knowledge of the user’s key.

Sicra and pre-authentication

Sicra delivers pre-authentication solutions both at the application/network level and within Kerberos-based identity environments. This way, organizations achieve both strong protection and a seamless user experience.

Services

Learn more about "Firewall" here >

Learn more about "Application delivery controller" here >

Learn more about "Zero Trust architecture" here >

Learn more about "Access management – Identity and access management (IAM)" here >

Learn more about "Multi-factor authentication" here >

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Pre-authentication

What is pre-authentication?

Sicra and pre-authentication

Services

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