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Exploring Various Delivery Methods for OTP Channels

Learn about OTP channels and their significance in delivering one-time passwords. Explore various methods of OTP delivery and their implications for enhanced security.
by Fazpass Indonesia
June 27, 2023
otp channels
OTP channels refer to the different methods or channels through which the One-Time Password (OTP) is delivered to the user for authentication purposes. These channels can vary depending on the platform, service, or system being used. The choice of OTP channel depends on various factors, including security requirements, user convenience, and the platform or system's capabilities. Additionally, users need to ensure that their registered contact information is accurate and up to date to receive OTPs through the appropriate channel. OTP channel meaning an application of service that the user uses. Such as SMS, Email, WhatsApp, and missed calls. Additionally, there are a few more channels that can be used as an alternative, but here we will discuss the most common ones only.

OTP Based on Channels

There are many channels available to help the user in getting OTP. Here are some of the most common channels available and how the OTP based on the channel works. From the initiation up to the verification and grant the access.


SMS OTP refers to the delivery of a unique, time-limited password to a user's mobile phone via SMS (Short Message Service). It is a widely used method for two-factor authentication (2FA) and provides an additional layer of security for online accounts, applications, and services. The SMS OTP typically works:
  • User Initiation: The user attempts to log in to a system or application
  • Delivery via SMS: The OTP is sent as a text message to the mobile phone number associated with the user's account. The OTP is typically a short numeric code, often consisting of 4-6 digits.
  • User Enters OTP: The user manually enters the received OTP into the appropriate field on the login screen or application.
  • Verification by Server: The server verifies whether the entered OTP matches the one it generated for that specific session.
  • Authentication Validation: If the entered OTP matches the OTP generated by the server, the authentication is considered successful. The user gains access to the desired system or application.
SMS OTP provides a convenient and widely accessible method of authentication. However, it's important to note that SMS OTP can have certain vulnerabilities. Such as the risk of interception through SIM swapping or phishing attacks targeting SMS messages.

2. Email OTP

Email OTP refers to the delivery of a unique password within a short period to a user's email address for authentication purposes. This method commonly uses two-factor authentication (2FA) and provides an additional layer of security for online accounts, applications, and services. Email OTP typically works with the same steps and process as SMS OTP. The difference is in the destination where the system sends the OTP. With email OTP channels, the OTP code will be sent to the email address given by the user. So, the user has to check their email inbox and find the email containing the OTP. The OTP is typically a short alphanumeric code. The next process is also the same as the SMS OTP channel. However, it's crucial to be cautious of phishing attempts targeting email communications. As malicious actors may attempt to deceive users into providing their OTPs through fraudulent emails.

3. WhatsApp OTP

As with the other OTP channels, such as SMS or email, the same process applied to WhatsApp accounts as well. The difference is the OTP is sent to the WhatsApp number of the user. The message contained the alphanumeric code within a certain short period. The next process will be the same as the other channels. However, it's important to note that WhatsApp uses end-to-end encryption for messages. That way, it will ensure that your communications are secure and private.

4. Missed Call OTP

Missed call OTP, also known as missed call verification, is a method of authentication that uses a missed call as a means to verify a user's phone number. Usually, the system uses this scenario where sending an SMS or email OTP may not be feasible. Here's how missed call OTP verification typically works:
  • User Initiates Verification: The user provides their phone number during the verification process of a service or application.
  • User Makes a Missed Call: The user initiates a call to the designated phone number given by the system or service. The call is disconnected automatically after a few rings before it is answered.
  • Verification Confirmation: The system or service detects the missed call from the user's phone number and confirms it as a successful verification.
  • Authentication Validation: Once the missed call is detected and confirmed, the system considers the phone number associated with the missed call as verified.
Missed call OTP verification offers a convenient and user-friendly method of authentication. Because it does not require the user to enter a code manually. Additionally, it leverages the phone's call functionality. Hence, making it accessible to users with basic mobile phones or limited internet connectivity. However, missed call OTP verification may have limitations and may not be suitable for all situations or regions. Some factors to consider include the availability and cost of making phone calls. Also, compatibility with different phone networks, and potential challenges related to missed call detection in certain circumstances.

Advantages of OTP Authentication

Advantages of OTP Authentication There are a lot of advantages to making authentication by OTP based on channel services. Usually, the channel chosen by the user will be the best way to deliver OTPs. Because that will be the most familiar and the fastest response that the user will give. Here are the other positive advantages of using OTP channels in making OTP authentication:

1. Safe from Re-Attacks

A replay attack occurs when an attacker intercepts a valid OTP and attempts to reuse it to gain unauthorized access to an account or system. OTPs are designed to be resistant to such attacks by being time-limited and usable only once, thereby enhancing the security of the authentication process.

2. Allows You to Perform Multiple Tasks

This is to emphasize the convenience, efficiency, and security given by OTP authentication. That enables users to navigate and engage in various activities within a system or application without the need for repetitive authentication steps.

3. Allows You to Protect Your Emails

By implementing OTP authentication, you add an extra step beyond the traditional username/password combination. This enhances the security of your personal information and helps prevent unauthorized access. Moreover, it adds an extra layer of protection against various types of attacks, such as password breaches, phishing, or brute-force attempts.

4. Convenient to Use

OTP authentication is often designed to be user-friendly and straightforward. Once you receive the OTP, you simply enter it into the designated field during the authentication process. Hence, this offers a convenient and user-friendly way to enhance security without sacrificing usability. OTP channels are indeed giving the way for authentication needed by a system. This will be the secure way to proceed with a process being done. That way, the user will be the only party that can do it and safely proceed with the login attempt or any transaction to be made.

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