Types of Authentication: Comprehensive Guide

Thierry Gagnon
Aug 21, 2023
Types of Authentication: Comprehensive Guide


To ensure that only authorized people have access to data, networks, applications, and online services, it is essential to have a robust authentication mechanism in place.

With many authentication methods available to the public, choosing the right one becomes crucial. Each method has its own set of usability, cost, and security trade-offs. In this article, we’ll explore the types of authentication, unraveling their unique
strengths and how they shape our digital experiences.

Understanding Authentication

Authentication is typically described as the process that confirms a claim of identity, verifying such claims made by users, systems, subjects, or principals.

It is distinct from the identification process, which generates the identity or label for which a claim is made. This is a separate issue altogether and poses its own security concerns, as it can weaken the effectiveness of authentication systems, particularly
since many current digital identity systems are not stringent enough.

Authentication is crucial for maintaining a secure digital environment, as it is impossible to safeguard resources without it. Insufficient authentication methods can inevitably lead to security vulnerabilities and issues. Unencrypted methods, weak passwords,
and single-factor authentication are examples of inadequate authentication.

Authentication Factors

Authentication factors are different categories of credentials used to verify a user’s identity during the authentication process. They are grouped into various categories based on the kind of information they require from the user. The five main categories
of authentication factors are:

Knowledge-based factor (Something you know)

These authentication factors rely on the information that the user knows. It is one of the oldest types of authentication and is typically used in combination with other authentication methods to enhance security. In short, knowledge-based authentication
challenges users to provide an answer to a question only they would know. Thus, the strength of this type of authentication depends on the secrecy and unpredictability of the answer. However, with modern brute force attacking methods and the looming
threat of quantum computers, knowledge-based authentication methods face increasing risks to its viability.

  • >Passwords
  • Personal Identification Numbers (PINs)
  • Security questions and answers

Possession-based factor (Something you have)

This type of factor involves something the user possesses, usually a physical device, as evidence used to authenticate. Examples include:

  • Smart cards and magnetic stripe card
  • Hardware tokens
  • Mobile devices used for receiving SMS codes or running authentication apps
  • USB security keys

These possession-based factors require the user to have something physically in their possession to authenticate. They are generally more secure than knowledge-based factors, as it is easier for a hacker to steal a shared secret than it is to gain access
to a physical device. They are typically used in conjunction with other authentication factors for increased security, as possession-based factors can be lost, stolen, or compromised.

Inherence-based factor (Something you are)

Also known as biometric factors, this factor involves biological and behavioral characteristics of an individual to verify their identity. In most instances, they are unique to each individual. The advantages of these authentication factors are
that they are difficult to steal or duplicate, as they are an inherent part of the individual. Examples include:

Due to their inherent uniqueness, inherence-based factors are considered highly secure. Like other factors they are not foolproof. They can be susceptible to false positives and negatives, sophisticated attacks, and can be affected by environmental conditions
or changes in appearance. Despite these limitations, due to their convenience and enhanced security, inherence-based factors are becoming increasingly popular. 

Location-based factor (Somewhere you are)

This factor uses the geographic location of the user as a form of authentication. It involves checking the user’s current location against known or expected locations to grant access to a system or resource. Examples include:

  • IP address geolocation
  • Network location
  • Bluetooth proximity
  • Near field communication (NFC)
  • GPS data from mobile devices
  • Geo-fencing

This is an example of contextual authentication, as the additional information is used in conjunction with traditional factors to enhance security. Location-based factors should not be relied upon as a sole factor but should be used to support a multi-factor
authentication (MFA) strategy.

Behavior-based (Something you do)

This factor relies on the real-time analysis of unique patterns of behavior exhibited by individuals during their interaction with digital devices or systems. Anomalies in user behavior are detected to prevent unauthorized access to resources.
Examples include:

  • Keystroke dynamics (typing patterns)
  • Mouse movement patterns
  • Gesture recognition
  • Voice behavior analysis
  • Gait analysis
  • Usage patterns

Like geographic-based factors, behavior-based factors should ideally be used in conjunction with authentication methods to establish a multi-layered approach to security.  

The advantage of using this type of factor is that they are passive and continuous, meaning that the user does not have to take any extra action to access resources. The system continuously monitors and assesses their behavior to enable seamless access.
Despite the advantage of a frictionless experience, privacy and data collection concerns arise. Behavior-based factors also face the drawback of potential false positives due to changes in a user’s behavior, caused by fatigue, stress, or other conditions.

Authentication Methods

In the digital era, securing information and ensuring the integrity of data access is paramount. Authentication methods act as gatekeepers, deciding who gets access to which data based on various verification techniques. These methods range in complexity and strength, with each one designed to cater to different security needs and scenarios. Two widely recognized and used methods are Single-Factor Authentication (SFA) and Two-Factor Authentication (2FA). While they both aim to protect data, they differ in terms of their approach and the layers of security they offer. Multi-Factor Authentication (MFA) offers an even more robust security solution that makes it harder for unauthorized users to gain access to systems, applications, or networks.

Single-Factor/Primary Authentication (SFA)

Single-factor authentication (SFA) can be defined as the process of securing access to a network or website by identifying the party requesting access only through one category of credentials. This might be anything that can be known (such as passwords), something that you are (such as a fingerprint or face recognition), or something that you have (such as a smart card or a device).

It’s worth highlighting that SFA only refers to the number of factors that are used, not to the type of authentication used—which is usually more important in terms of security. However, for the average user, SFA is widely considered to be a weaker method regardless of the factors that are involved. For such reason, it should be used only when MFA is not possible. 

Two-Factor Authentication (2FA)

Two-Factor Authentication (2FA) is a method where users need to provide two pieces of verifiable information to be granted access. This method was created to add an additional security layer to data protection. However, as mentioned above, a 2FA is not necessarily more secure than an SFA.

In order for 2FA to be effective, the two pieces of information required to authenticate must be different in nature. For example, a 2FA may require users to provide usernames and passwords as well as fingerprints to access a system or an application. Another example could be a 2FA that requires users to provide their usernames and passwords as well as proof that their smartphone is in their possession (usually through SMS or an app).

Multi-factor Authentication (MFA)

Multi-factor authentication (MFA) is a method where users need to provide more than one piece of verifiable information to access a system, application, or network. Similar to 2FA, this method was created to add an additional security layer to data protection. To be precise, 2FA is actually considered a MFA method because it requires more than one credential to sign on. However, many MFA systems often require more than two credentials to increase security. Like 2FA, the verifiable information must also be different in nature. For example, you may need usernames and passwords, as well as a fob and a fingerprint.

Authentication Standards and Protocols

Ensuring a secure and seamless user experience is paramount in this digital age. Several authentication standards and protocols have emerged to standardize methods for verifying user identities and granting access to systems or data. Some of the most influential and widely adopted standards include:

SAML Authentication

Security Assertion Markup Language (SAML) is an open federation standard that is used for sharing information about the authentication process. Security Assertion Markup Language usually leverages the Extensible Markup Language (XML) standard to share data. SAML provides businesses with a system for implementing SSO and other federated protocol systems.

SAML is usually a web or cloud-based application and it’s a particularly powerful tool for identity providers and service providers. There are usually three categories of entities:

  1. Users: Those trying to access a resource
  2. Identity Providers: Those authenticating the user and providing an assertion that contains user information.
  3. Service Providers:Those offering the resource.

OAuth 2.0

OAuth 2.0 is primarily an authorization protocol that allows third-party applications to access a user’s data on a resource server without needing to share the user’s credentials. However, it does not provide any standard mechanism for authentication, which is the process of verifying a user’s identity.

OpenID Connect

OIDC is a layer built on top of OAuth 2.0 providing an authentication system with a new type of token: the ID token. This token provides information about the authenticated user, allowing third-party applications to verify the user’s identity.

By extending OAuth 2.0 with these features, OpenID Connect provides a standardized way to authenticate users and access their profile information while maintaining the benefits of OAuth 2.0 for authorization. This makes OIDC a powerful tool for implementing single sign-on (SSO) solutions across multiple applications and services.

FIDO2 Standards and Protocols

Developed by the FIDO (Fast IDentity Online) Alliance, this standard focuses on providing stronger authentication through passwordless solutions. This industry consortium aims to create a more secure and user-friendly authentication experience by eliminating the vulnerabilities associated with password use. These advantages are driving adoption among organizations and web services.

FIDO2 uses a combination of hardware (security keys), biometrics, and mobile devices to enable users to authenticate to online services. It comprises of two main components:

  1. WebAuthn (Web Authentication): This web standard is integrated into web browsers and platforms to enable passwordless authentication. With WebAuthn, users can register and authenticate using biometric devices, mobile phones, FIDO security keys or other authenticators.
  2. CTAP (Client to Authenticator Protocol): This protocol enables external devices to act as authenticators for web services. CTAP allows smartphones or security keys to work over USB, NFC, or Bluetooth.

Other authentication standards and protocols include:

  • JWT (JSON Web Token)
  • Kerberos
  • NTLM (NT LAN Manager)
  • RADIUS (Remote Authentication Dial-In User Service)
  • LDAP (Lightweight Directory Access Protocol)
  • CHAP (Challenge-Handshake Authentication Protocol)

Together, these standards and protocols form the backbone of modern digital authentication, each catering to specific challenges and user needs.

Authentication Types

From traditional password-based authentication to cutting-edge biometric and multi-factor authentication, there is a range of authentication techniques designed to verify user identities and grant appropriate access privileges. Here are some of the most popular types of authentication:

Password Authentication

Despite their obvious vulnerability and security risk, password authentication have been the cornerstone of digital security for decades. Built on something a user knows, passwords use a unique combination of letters, numbers, and special characters to authenticate users in the most basic of forms. Therefore, their biggest strength relies on the complexity, with a strong password usually having 12 or more characters, with a mix of characters, uppercase letters, numbers and special symbols. Even extended strings of just letters or words, if long enough and random, can provide sufficient levels of security against unauthorized access.

Passwords, a thing of the past?

Passwords are a tried-and-true favorite, providing a simple mechanism to “securely” authenticate users with widespread acceptance. Yet, it seems it is only a matter of time before passwords become extinct. With the continuous rise of cybercrime, passwords are being targeted as one of the most vulnerable points of attack and are breached everyday by brute force, phishing, social engineering, and other common attacks.

The Imperative of Strong Password Practices

Taking into account the pitfalls of passwords, it’s critical for organization and user to employ strong password practices. That means creating and managing secure and unique passwords for the different platforms you use and periodically updating. Furthermore, with the current state of cyber threats, secure password habits are now not just a recommendation, but a clear necessity for maintaining a secure digital environment.

Biometric Authentication

In simple terms, biometric authentication is a specific type of authentication that uses physical or behavioral traits to detect and authenticate the identity of a user trying to access applications and other network resources. More specifically, these physical and behavioral traits are used to create a data-generated model that represents the user and is authenticated against. Some of the most common types of biometric authentication deployed today include:

  • Fingerprint Recognition: Uses the unique patterns and ridges of a user’s finger.
  • Facial Recognition: Employs algorithms and imaging to distinguish and validate facial features.
  • Iris Scanning: Analyzes patterns in the colored segment of a user’s eye.
  • Voice Recognition: Identifies individuals using unique voice tonalities.

During the past years, biometric authentication has quickly become a commonly deployed element in multifactor and passwordless authentication strategies as it provides high levels of security with a friendly user experience and easy integration. Biometric systems, however, do have their limitations, which are largely centered around privacy concerns as well as system efficiency and potential implementation costs.

Passwordless Authentication

The password problem is not something new, thus there are already several modern authentication solutions that protect organizations and their users against the most common attack vectors. Among these, passwordless authentication stands out at the forefront of new and innovative authentication methods.

Instead of primarily relying on knowledge-based authentication, like we see with alphanumerical password codes, passwordless authentication leans on more reliable factors like biometric data validation and secure cryptography. Some popular examples of passwordless authentication methods include biometric authentication, security/hardware tokens, smart cards, mobile authentication apps, QR codes, magic links, one-time passwords (OTP), and NFC devices.

Passwordless authentication is clearly the way of the future, in fact many of us have been using passwordless methods for many years now. So, what makes passwordless so great? We can summarize this into two main advantages of passwordless systems:

  • Enhanced Security: By removing passwords, passwordless authentication eliminates today’s most common attacks like phishing and presents a much more secure mechanism of user validation.


  • User Convenience and Reduced Friction: Passwordless authentication brings a new level of convenience to user logins, with a simple process that is faster than typical password-based and 2FA/MFA options and removes the need to remember and manage a database of complicated passwords. This can lead to higher user engagement and satisfaction, and easier password recovery and customer service processes.

Token Authentication

Token authentication is a method that aims at simplifying login processes for known users. With this method, users send a request to a server using a traditional username and password combination and, upon validation, are issued an authentication token. Subsequent authentication requests are then authorized with this authentication token, rather than consistently prompting users for their username and password. Examples of the different types of tokens and protocols that are used by this system include:

  • Cryptographic Tokens
    : These tokens, which are frequently hardware-based, contain cryptographic algorithms and keys. They give an additional layer of encryption-based protection to the authentication process by generating codes or verifying user credentials.


  • JSON Web Tokens (JWT) and OAuth: These widely accepted protocols and standards support the implementation of token-based authentication, ensuring seamless system integration.

By removing the need for users to repeatedly insert their credentials, token authentication creates several benefits for organizations and users. This includes advantages like increased security with transient access and revocability, enhanced user experience by streamlining the login process, and scalability for expanding user bases without compromised performance or safety.

API Authentication

Application Programming Interfaces (APIs), which enable a wide range of interactions between various programs, are found at the junction of contemporary digital ecosystems. Securing these conversations becomes essential because sensitive data transfers are frequently involved. Enter API authentication, a safety net that verifies the parties involved in these transactions and ensures their legitimacy before transferring any data. Common API authentication systems include:

  • HTTP Basic Authentication: This method is rather straightforward and combines a username and password with Base64 encoding before sending it over an HTTP header. It’s simple, but because it relies on simple encoding, however, it is usually not the most secure.


  • API Key Authentication: Consider API key authentication as a digital passport. With this system, authentication request headers contain an API key, which is a distinctive string of digits and letters. Servers verify this key against their records, and if verified, permit access, thus adding an extra degree of security.


  • OAuth Authentication: This approach is more reliable and adaptable. Platforms that support OAuth give third-party programs restricted access to user accounts without disclosing passwords or other sensitive information.

One of the main benefits of API-based authentication systems is secured data exchanges, which, by verifying the entities involved in data transfers, minimizes the risks of unauthorized access. API authentication systems also offer flexible access control; for instance, with OAuth, users can determine varying degrees of access based on their preferences and consent.

Single Sign-on (SSO)

We can define Single Sign-On (SSO) as an authentication process that enables users to log in to different applications using just a single set of credentials. The most significant advantage of SSO is its capacity to simplify the user experience, removing the need to remember several passwords while bolstering security, optimizing productivity, and providing centralized management. To elaborate on that, here are the top benefits of implementing an SSO system:

  • Streamlined Authentication: Easy access to multiple applications with one set of credentials.


  • Enhanced User Experience: Seamless login experience with one authentication prompt.


  • Bolstered Security: Reduced vulnerability and attack surface through the elimination of multiple authentication points.


  • Optimized Productivity: Increased user efficiency from easy navigation between platforms without multiple logins.


  • Centralized Management: Improved compliance and security through a consolidated oversight of user access.

For these reasons, SSO has become common practice across all tiers of organizations and enterprises – typical use cases of SSO include:

  • Cloud Applications: With the popularity of cloud-based applications in business, SSO has positioned itself as an easy tool to effortlessly switch between cloud services like CRM, email, and other collaboration tools.


  • Enterprise Systems: For large corporations with many applications, SSO is a perfect solution to simplify entry to HR systems, intranets, and other proprietary systems.


  • Consumer Platforms: SSO is well suited to help organizations enable a seamless experience for their users to access all of their products and services with one login.

Adaptive Authentication

This is technically not a type of authentication but an additional security measure built on top of some of the other methods in this list.

Also known as contextual authentication, adaptive authentication brings a risk-based scoring approach to authentication. More specifically, it dynamically selects authentication factors based on contextual and user behavioral cues to ensure appropriate security levels. Adaptive authentication prevents low-risk activities from burdening the security network and makes high-risk operations more challenging to hack. Examples of the contextual and behavioral factors considered include:

  • Behavioral Analysis: These systems learn user behaviors and flag deviations; for example, user location access points serve as a typical data point that would raise potential red flags if a user were to attempt to log in from a different country.
  • Risk Factors: Risk factors like connection type, geolocation, and device recognition are typically assessed by adaptive systems and used to adjust authentication processes on-the-fly.

Adaptive authentication also enables lower false-positive rates, so businesses can enjoy improved user experience, and potentially higher long-term revenue, thanks to better efficiency and security. An example of how adaptive authentication provides value in practice is in the banking industry, where it ensures secure transactions. For example, if a customer conducts typical transactions, a password may be sufficient. But for unusual or large transactions, additional verification, such as a one-time code or fingerprint scan, and adaptive risk assessments may be required. This tailored approach provides robust security and a seamless banking experience.

Out-of-Band Authentication (OOB)

Out-of-band authentication (OOB) is a 2FA where a secondary verification method is required on a separate communication channel. Usually, OOB systems have two different channels: the first one is the users’ internet connection, and the second one is the wireless network their phone connects to. The more segregated the two channels are, the greater the security benefits. This reduces the risk of both channels being compromised at the same time, which can provide overall greater security when compared to login attempts using a single-band system.

Methods of OOB Authentication:

  • SMS Verification: The user receives a one-time password (OTP) or verification code sent via SMS after initiating a login. The code must then be entered into a website or application to complete the process and gain access to a resource.


  • Email Verification: Similarly, a verification link or a unique code is sent to a user’s registered email address. Access is granted once the user correctly provides this information or clicks on the link.

OOB authentication augments traditional security practices by harnessing disparate communication channels and offers a more robust defensive stance against cyber threats. It is imperative that the choice of channels be carefully chosen as they are not all equivalent (e.g. SMS vs App base OTP, the latter usually being a more robust alternative). It also goes without saying that the way to access these communication channels should be considered. All too often, the organization relies on mobile devices to do OOB, but they become of little use if the mobile device itself is compromised. Ideally, it would require two completely segregated channels accessed via two separate devices where one doesn’t offer external connectivity capabilities.


You’ve probably encountered CAPTCHAs while navigating the digital world; they frequently appear as distorted letters or image choices on web forms. The Completely Automated Public Turing Test to Tell Computers and Humans Apart, or CAPTCHA, is a tool used to distinguish between legitimate human users and the automated bots that wreak havoc on the internet.

CAPTCHAs are essential for maintaining online security. They serve as a gatekeeper, guaranteeing that only legitimate human users can access online services by posing tasks or challenges that are easy for humans to complete but notoriously difficult for robots, such as decoding distorted characters or identifying particular images in a grid.

CAPTCHAs have established themselves as a potent deterrent against automated attacks, including spamming and brute-force login attempts. They increase the safety of websites and online platforms by requiring human input and preventing bots from carrying out planned actions.

In essence, even though CAPTCHAs can occasionally seem a little annoying, their significance in guaranteeing a safer, bot-free online experience cannot be denied.

The basic concept behind CAPTCHAs is that the tests provided are simple for people to complete but difficult for robots. By introducing an additional layer of verification, CAPTCHAs strengthen internet security and confirm authentic users.


Advantages of Implementing a Robust Authentication System

There are several reasons why you would want to implement robust authentication systems in your daily operations:

  • Better security: having a solid system in place will significantly decrease the risk of unauthorized access to your network. Almost every existing business might need to have a secure system in place to protect its IT infrastructure;
  • Sensitive information: for all those businesses that deal with information that should not be shared with the public and that will be harmed by their data leaking, it’s crucial to leverage a strong system to protect sensitive information;
  • Preserving privacy for users: companies and organizations that deal with data and information of their users should put strong methods to preserve their privacy and protect the company’s reputation;
  • User experience: businesses need to better understand how the process works so that they can avoid sacrificing the usability of their product and reduce friction as much as possible.

Factors to Consider When Choosing Authentication Methods

When considering which type of authentication you should be using or implementing for your business, several factors need to be considered:

  1. It’s important to evaluate the scalability and compatibility of a method with existing systems. Context matters and every company and environment will be able to effectively integrate only a specific set of authentication systems.
  2. Especially for B2C and consumer-facing companies, it’s particularly crucial to evaluate user convenience and ease of implementation, since sometimes better security can be at the detriment of usability for the end user.
  3. It’s also essential to consider cost-effectiveness and maintenancerequirements when choosing different types of authentication.


Gone are the days when a simple password was enough to secure our virtual fortresses. It is now imperative for organizations to implement suitable authentication systems that ensure robust security. Companies need to better understand their authentication needs and only then pick the systems that best align with their cybersecurity goals.

From passwords to MFA and passwordless, a wide range of methods can be used to ensure that malicious third parties do not access critical data. In today’s digital environment, MFA, passwordless, and biometric authentication are taking over for secure authentication, especially for organizations that put security, privacy, and ease of use first.

At Kelvin Zero, we are going beyond this by building next-gen authentication and trust solutions to help secure organizations through our digital future. Authentication stands at the forefront of this mission, which is why we built, Multi-Pass, a global authentication solution with built-in offline biometrics and proprietary cryptography, to eliminate passwords and enable the future of authentication. Contact us today and set up a demo to learn more about Multi-Pass and how Kelvin Zero can help you integrate trust throughout all of your operations.

Thierry Gagnon

Thierry is co-founder and CTO of Kelvin Zero and one of the world's foremost experts on secure information sharing networks. With expertise in the development of automated systems, cyber knowledge bases, malware analysis & reverse engineering, and cyber threat intelligence, we are grateful to...