HOTP vs TOTP: What's the Difference?

HOTP vs TOTP: What's the Difference?
HOTP vs TOTP: What's the Difference?

Network security is dependent on authorisation through verification, identification, and authentication of user identity. Hence, it is safe to say that the authentication process is one of the most essential procedures the security system has to consider. One such authentication procedure is SMS authentication.

SMS authentication has three sections: OTP, TOTP, and HOTP. The one-time password mechanism was a huge revelation to the digital security industry. It was used as the second layer of the two-factor authentication process. However, OTP has two more variants! HOTP and TOTP!

In this blog, we are going to talk about these two types of OTP and understand the difference between these two: HOTP vs TOTP.

What is HOTP?

HOTP stands for HMAC-based one-time password, and HMAC is short for Hash-based Message Authentication Code. This means that HOTP is basically a Hash-based message authentication code-based one-time password.

HOTP operates on a cryptographic function. This cryptographic function works in integration with a shared secret key that generates an OTP.

The catch is that this process involves a counter value with the secret key through the HMAC algorithm. This process creates a unique authentication code. After every authentication attempt, the counter value of the authentication code changes, ensuring the uniqueness and distinction of each password.

It is a valuable addition to the OTP family since it ensures proper authentication and a straightforward approach.

What is TOTP?

TOTP stands for Time-based One-Time Password, and as the name suggests, it is a time-sensitive OTP. This basically means that the one-time password provided by the security system will be invalid after the designated time, which usually ranges from 30 to 60 seconds.

This time-bound approach can be extremely beneficial for the security procedures and protocols of the organisation’s network. The TOTP brings various benefits to the table, but it also has a few limitations. However, these benefits outweigh the limitations.

Let us look at the various differences between HOTP and TOTP.

Difference Between HOTP and TOTP

Let us understand the difference between these two types of OTPs with the help of the features they provide to your authentication system.

HOTP vs TOTP – Functioning

  1. TOTP: Time-based one-time password pretty much sums up the function of this type of OTP. A system-generated password that is valid for one-time use and also needs to be entered into the system in a limited time frame of 60 seconds.

This OTP is generated in the mobile device as well as the system at the same time to verify the user's identity.

2. HOTP: The process begins with a system-generated password that is known only to the user and the server. The counter value, usually the last number, increments or changes after each authentication attempt to ensure a unique OTP each time.

The HMAC algorithm helps combine these numerical values to create the secret password. When the user enters the password in the system, the server verifies it to accept or reject access.

HOTP vs TOTP – Generation Mechanism

  1. TOTP: The time-based OTP system generates the secret passcode based on the current Unix time. The code is then based on the TOTP algorithm, ensuring that every time, the system generates a unique and new OTP for every other user.
  2. HOTP: On the other hand, the OTP code is generated using a counter-based approach. This code uses a secret key, cryptographic technologies, and a counter-value that increments after every authentication attempt.

HOTP vs TOTP – Replay Attacks

  1. TOTP: The biggest threat to OTPs is replay attacks. Replay attacks commonly happen with the standard OTP. However, TOTP is highly resistant to replay attacks.

The major reason behind this is the nature of the code that is generated. The code is time-sensitive, and hence, the attacker doesn’t get enough window of opportunity to attack.

2. HOTP: With HOTP, the OTP code is unique but static, nonetheless. Until and unless the counter value increments, the OTP remains static, and that can give an attacker a long time to perform the replay attack. Hence, we can say that the HOTP does not carry resilience towards replay attacks.

HOTP vs TOTP – Implementation

  1. TOTP: TOTP is very straightforward regarding implementation and integration with multi-factor authentication. Along with the implementation angle, there is the user’s angle, too. The users find it relatively easy to navigate through the authentication process, making it a customer favourite.
  2. HOTP: Implementing HOTP can lead to additional overheads due to the complexities of counter-value incrementation. The considerations for managing and synchronising the server and user device become complex. It also complicates the deployment of this mechanism in specific environments.

OTP vs TOTP – Which is Better?

If you want ease of use, user-friendliness, straightforward implementation, comprehensive security, etc., you can opt for TOTP. Whereas, if you want robust security and a counter-based approach, you can definitely go for HOTP.

The choice between HOTP and TOTP can be answered by the organisations themselves. It totally depends on their requirements. However, we can say that TOTP is slightly better and more straightforward than HOTP!


In conclusion, we can say that the choice between HOTP and TOTP is highly based on the needs and preferences of those particular security systems. Before implementing any of these mechanisms, several practical considerations must be considered. These considerations might include budget, storage, bandwidth, etc., and these factors influence the decision.

Integration of these mechanisms with two-factor or multi-factor authentication can do wonders. All you need to do is find a service provider that provides high-quality services, like Instasafe!

Frequently Asked Questions (FAQs)

Can HOTP and TOTP be used interchangeably in two-factor authentication?

Yes, but even when both, HOTP and TOTP are utilised for authentication purposes, these two technologies or terms cannot be used interchangeably. The choice between these two technologies will be solely in the hands of the organisation.

Which method is easier to integrate with your authentication system and also user-friendly?

TOTP can be considered as a more user-friendly and integrable mechanism due to its familiarity and ease of use. This contributes to an accessible and straightforward experience both ways.

Which method resists replay attacks the most?TOTP is more resistant to replay attacks since it is time-sensitive. Between HOTP vs OTP, TOTP stands to prevent a greater number of replay attacks.