What Is a One-Time Password (OTP) in Payment Authentication?

A one-time password, or OTP, is a short temporary code used within a single authentication step, such as during payment verification. Usually, receiving an OTP shows that the user has access to the method registered for authentication, like their phone or email.

OTP自体はアカウントの所有権をチェックするものではなく、プロセスを現在のデバイスやサービスに紐づけるものです。これらのコードは、短い期間有効であるか、認証に使用されるまで有効で、その後システムはそれらを無効と認識します。有効期間が短いことで、コードが複数回入力される可能性が低くなります。コードが有効な間は、もし誰かが傍受すれば、この期間内に使用される可能性があります。その結果、OTPのセキュリティは、全体的な認証プロセスにどのように組み込まれているかに依存します。

A static password remains valid for repeated logins until you choose to update or reset it. In comparison, an OTP is intended for single use, generally becoming inactive once entered or when its brief validity period is complete. When OTPs from previous sessions have already been entered or have expired, they are simply recognized as inactive by the system.

Using OTPs as the main method addresses specific scenarios, but it is important to note they are not designed to handle every situation, such as when a code is given input through different sites or platforms while still within its time window. An attacker who obtains a valid code while it is still active may attempt to use it immediately.

OTP generation and OTP delivery are separate concepts. HOTP and TOTP define how codes are generated, while SMS, email, and voice describe channels through which a code may be delivered.

Authenticator apps can generate TOTP codes on the device itself, making the code available locally rather than relying on a separate message or network communication for each use. There’s also push authentication, which lets users approve access through a prompt instead of entering a code.

In an EMV 3-D Secure (3DS) flow, the system may sometimes prompt for extra confirmation from the person making the purchase. The issuer’s Access Control Server (ACS) might review the transaction and decide if more steps are needed to verify the user’s identity.

One option is an OTP, which is usually sent to the cardholder through a registered channel such as a text or email. The individual then types this temporary code into a verification box that appears during payment. Other approaches, like receiving a request in a banking app, can also be used for this part of the process.

After the required authentication is marked successful, the transaction continues with the next stage of payment processing.

At a glance, OTP, MFA, and SCA each point to different features of the authentication process. Here’s a quick rundown:

• OTP: a single-use code that helps verify identity during a specific interaction. Where it falls in the classification can depend on the technology involved, along with how the code reaches the user.
• MFA: 多要素認証, meaning the process uses more than one type of verification, like something you know, something you have, or someone you are.
• SCA: 強力な顧客認証. This is a requirement under European payment rules, generally calling for two (or more) separate verification elements, usually chosen between knowledge, possession, and inherence factors.

When applied on its own, an OTP generally provides one layer of authentication and would typically be combined with other factors to align with MFA or SCA requirements. However, an OTP may act as one element in a multi-factor setup, and in some cases, how you access your OTP might need a second verification step.
For remote electronic payments subject to SCA, there are often further requirements, such as linking the authentication code to details like the payment amount and who gets paid.

When looking into OTP options for payment authentication, companies usually check a mix of practical areas. Security usually gets attention, along with how easily codes reach users, whether the solution fits into current systems, and how it feels for people actually using it.
Each delivery method needs something different: SMS and voice depend on telecoms, while app-based codes run on enrolled devices without the phone carrier but need a one-time setup.
Some things companies might do are:

• Track the success rates of authentication steps, separating data by location and channel.
• Keep records of how often codes time out, how many retry attempts users make, and how various authentication attempts progress.
• Plan and document what alternatives are available in case the main option won’t work for someone.
• Assess factors such as potential phishing and how each approach works during account recovery situations.
• Check how each way of handling authentication lines up with requirements for 3DS, MFA, or SCA when those apply.

To get a useful perspective, teams often look at the entire authentication experience – not just OTP code delivery as a single part, but as one link in the user’s overall payment process.