What is a One-Time Passcode (OTP)?

A One-Time Passcode (OTP) is a unique, temporary password that is valid for only one login session or transaction. Unlike a traditional static password that remains the same until the user changes it, an OTP expires almost immediately after use or after a very short window of time (often 30 to 60 seconds), making it significantly harder for attackers to exploit stolen credentials.

Key components of OTP

OTP systems rely on three primary mechanisms to generate and validate codes:

• Generation Method: The code is created either by a server (time-based) or by a counter (event-based).
• Delivery Channel: The way the code reaches the user, typically via SMS, email, voice call, or an authenticator app.
• Validation Engine: The backend server that verifies the code against the expected value before granting access.

Types of OTP

OTPs can be generated and delivered in different ways, depending on the authentication method and security requirements. The three most common types include:

• Time-based OTP (TOTP): The most common form used by authenticator apps. A secret key combined with the current time generates a new code every 30–60 seconds.
• Event-based OTP (HOTP): A code generated based on a counter—each time the user requests a new code, the counter increments, and the code changes.
• SMS/Email OTP: A code sent to the user’s registered device. While convenient, these are considered less secure due to risks like "SIM swapping" or email interception.

Benefits of OTP

OTPs add a dynamic layer of protection to authentication workflows. By generating codes that expire quickly or can only be used once, OTPs reduce the risks associated with static passwords. Here is how:

• Protection against stolen credentials: If a hacker steals an employee’s primary password, an OTP serves as an essential second layer of defense. Since the attacker doesn't have access to the user's physical device or authenticator app, the stolen password is useless.
• Reduced risk of replay attacks: In a "replay attack," a hacker intercepts a user's data transmission and reuses it to gain access. Because an OTP is valid for only a single use, it cannot be intercepted and "replayed" to bypass authentication.
• User-friendly security: Most users are already familiar with receiving codes via text or authenticator apps. This low barrier to entry ensures that security protocols don't hinder daily productivity.

Comparative analysis

OTP vs. Static password

A Static Password is a long-term credential that is highly vulnerable to phishing, credential stuffing, and data breaches. An OTP is a short-term, disposable credential, providing a "fail-safe" that protects accounts even if the static password is compromised.

OTP vs. Hardware Token

A Hardware Token (like a YubiKey) is a physical device that generates an OTP or provides a cryptographic signature. While hardware tokens are more secure (as they cannot be intercepted via software), software-based OTPs (like those in authenticator apps) are more scalable and cost-effective for large organizations.

How to to deploy OTP securely
OTP requires more than simply turning the feature on. To reduce authentication risk without disrupting users, follow these practical steps:

1. Prioritize authenticator apps over SMS: Whenever possible, move users to TOTP-based authenticator apps. They work offline, generate time-based codes locally, and are less vulnerable to SIM swapping or SMS interception.
2. Integrate with Single Sign-On (SSO): Configure your SSO provider to require OTP during login, particularly for sensitive systems and high-risk accounts.
3. Enable rate limiting: Limit the number of OTP entry attempts before temporarily locking the account to reduce brute-force risk.
4. Set short expiration windows: Configure OTPs to expire quickly. Shorter validity periods reduce the opportunity for interception or misuse.
5. Educate users about phishing risks: Train employees never to share OTP codes (even with someone claiming to be from IT) as attackers often attempt to socially engineer one-time codes in real time.

Manage your access and security with Deel IT

Securing your team's access is a top priority for any global company. Deel IT helps you standardize security across your entire organization by centralizing device management and access controls. We ensure your global team—whether they are full-time Employees or independent contractors—uses secure authentication methods like OTPs and SSO to access company resources.

From automated onboarding to secure offboarding, Deel IT provides the oversight you need to maintain a compliant, secure environment. Learn more about how Deel IT secures your workforce.

Book a demo with Deel IT now.

FAQs

What if I don't receive my OTP? Network latency or issues with the delivery channel (like a delayed SMS) can cause OTPs to fail. This is why authenticator apps (TOTP) are preferred, as they generate codes locally on the device and do not rely on cellular networks.

Are OTPs enough on their own? OTPs are excellent as a second factor, but they should never be the only defense. They are most effective when part of a broader Multi-Factor Authentication (MFA) strategy that includes strong password policies and Zero Trust principles.