One-time passwords (OTPs) are a popular method for adding an additional layer of security to secure access, transaction authorization, and other purposes. Two popular methods of delivering OTPs are via SMS and email. In this article, we will discuss the theory behind how SMS and email OTPs work and compare the advantages and disadvantages of these methods.
SMS OTP:
When a user requests an SMS OTP, identity provider service generates a random code and sends it as an SMS via SMS service provider to the user’s phone number. The user then enters the code into the validation form, which is sent to identity provider for verification. Identity provider compares the code entered by the user to the code generated by the system and returns a success or failure message.
Advantages:
- Easy and convenient to use: SMS OTPs are widely supported, easy to use, and don’t require an internet connection. This makes them a practical option for users in areas with limited internet connectivity or where smartphones are not widely used.
- Reliable: SMS messages are delivered almost instantly, making SMS OTPs very reliable. The delivery time of SMS is relatively stable, and it does not depend on internet connectivity or server status. This means that SMS OTPs are not affected by downtime, maintenance, or congestion on the internet or servers.
Disadvantages:
- Costly: SMS OTPs can be costly, as each SMS sent for verification is charged by service providers. This can make SMS OTPs a more expensive option than email OTPs for high-volume use cases.
- Security risks associated with phone number verification: SMS OTPs rely on phone number verification, which can be vulnerable to security risks such as SIM swapping. This means that SMS OTPs may not be the most secure option for high-risk applications.
- Limited message length: SMS messages have a maximum length of 160 characters, which can limit the amount of information that can be conveyed in an SMS OTP.
Email OTP:
When a user requests an email OTP, identity provider service sends a message to the user’s email address with a unique code. The user then enters the code into the validation form, which is sent to the identity provider for verification. The identity provider compares the code entered by the user to the code generated by the system and returns a success or failure message.
Advantages:
- More cost-effective solution: Email OTPs are generally more cost-effective than SMS OTPs, as there is no charge per message. This makes email OTPs a more practical option for high-volume use cases.
- Widely supported: Emails are a widely supported technology, which means that Email OTPs can be received on any device with an internet connection, making them more accessible than SMS OTPs.
- Easier to use for users with limited access to a phone or internet connection: Email OTPs can be accessed on any device with an internet connection, making them a practical option for users with limited access to a phone or internet connection.
Disadvantages:
- Security risks associated with email accounts: Emails can be intercepted or redirected, email accounts can be compromised through phishing or malware attacks. This means that Email OTPs may not be the most secure option for high-risk applications.
- Delivery time: Email delivery times can vary widely depending on the email provider, network status, and email settings. This means that Email OTPs may not be as reliable as SMS OTPs, especially if the user is in an area with poor internet connectivity.
- Spam and junk filters: Emails can be filtered as spam or junk, which can cause Email OTPs to be missed or delayed. This can be frustrating for users who are waiting for an OTP to complete an important transaction or access a service
In conclusion, SMS and email OTPs are two widely used methods for secure access and transaction authorization. SMS OTPs are easy to use, reliable, and don’t require an internet connection, making them a practical option for users in areas with limited internet connectivity or where smartphones are not widely used. However, SMS OTPs can be costly, and phone number verification can be vulnerable to security risks.
On the other hand, email OTPs are a more cost-effective solution and can be accessed on any device with an internet connection, making them more accessible than SMS OTPs. However, email accounts can be compromised through phishing or malware attacks, and delivery times can vary widely depending on the email provider, network status, and email settings.
Ultimately, the choice between SMS and email OTPs depends on the specific use case and the level of security required. While SMS OTPs may be more convenient and reliable, they may not be the most secure option for high-risk applications. Similarly, while email OTPs may be more cost-effective and accessible, they may not be the most secure option for applications that require a high level of security. Therefore, it is important to carefully consider the advantages and disadvantages of each method before selecting the appropriate method for a specific use case.
