When it comes to Two-Factor Authentication (2FA), one-time passwords (OTPs) are widely used to secure online accounts. While SMS-based verification codes are the most common, they’re not the most secure. In contrast, Time-based One-Time Passwords (TOTP) and HMAC-based One-Time Passwords (HOTP) are increasingly being used for better security in OTP generation.
These methods are not only more secure but also harder for hackers to bypass, providing enhanced protection for your digital identity.
In this article, we will break down what TOTP and HOTP are, the key differences between them, and why they are the most secure forms of 2FA for online authentication.
Both TOTP and HOTP are much more secure than SMS-based OTPs, but there are a few differences between the two in terms of security and functionality:
1. Time Sensitivity in TOTP vs. Counter-based in HOTP
The most notable difference between TOTP and HOTP is how the OTPs are generated:
TOTP passwords are time-sensitive, typically valid for about 30 seconds. After the time expires, the code becomes invalid, even if the user hasn't entered it yet. This short validity window adds an extra layer of security because it reduces the chances of an attacker using a stolen OTP.
HOTP, on the other hand, is counter-based and does not expire after a short time. Once the code is generated, it remains valid until it is used. While this is still more secure than SMS-based OTPs, the lack of time expiration makes HOTP a bit more vulnerable to attacks like man-in-the-middle if the attacker has access to the counter.
2. Time Synchronization in TOTP vs. Counter Synchronization in HOTP
TOTP requires both the server and user’s device (usually the authenticator app) to be time-synchronized. This ensures that the password is valid for a brief period and cannot be reused. Time-based synchronization adds a layer of protection because an attacker needs to have access to the exact time synchronization to generate valid OTPs.
HOTP doesn’t require time synchronization but depends on counter synchronization. While this system is secure, it can be vulnerable if the counter is somehow out of sync between the server and user. In scenarios where there is a misalignment, users may have to reset the counter, which can introduce security gaps if handled incorrectly.
While SMS-based OTPs are the most commonly used form of 2FA, they come with inherent vulnerabilities:
SIM swapping: Attackers can trick mobile carriers into switching the victim’s phone number to a new SIM card, gaining access to SMS-based OTPs.
Message interception: SMS messages can be intercepted by hackers using methods like Stingray devices that mimic cell towers.
In contrast, TOTP and HOTP provide more secure OTP generation because:
TOTP is time-sensitive, making it harder for attackers to reuse OTPs.
HOTP is counter-based, making it more difficult for attackers to predict or reuse generated codes.
Both methods do not rely on mobile networks, unlike SMS-based codes, which are susceptible to network-based attacks.
TOTP is ideal for time-sensitive applications where the user needs to enter a code that is valid only for a short period. This is perfect for scenarios where rapid authentication is needed, and where offline functionality is a key feature, such as logging into banking apps or email accounts.
HOTP is suitable for situations where you don’t want time-sensitive authentication but still need a secure method to generate unique passwords for each login attempt. It works best in scenarios where consistent synchronization between the server and user is maintained, such as for internal enterprise applications or hardware tokens.
In the evolving landscape of cybersecurity, using TOTP or HOTP for 2FA offers one of the most secure ways to authenticate online. TOTP is ideal for applications that require time-sensitive codes, while HOTP serves as a secure alternative when counter synchronization is preferred. Both methods offer significant advantages over SMS-based OTPs, making them essential for securing sensitive data.
By leveraging these secure OTP generation methods, you can ensure that your accounts and personal data are safeguarded from hackers, even if they have your password.
