What is Two-factor authentication?
Two-factor authentication which is also referred to as Two-Step Verification is a process involving two subsequent but dependent stages to check the identity of an entity trying to access services in a computer or in a network with just one factor or secret. Without 2 Factor Authentication, you enter in your username and password, and then you're done. The password is your single factor of authentication.

What is the benefit o f Two-factor/Two-Step Verification?
The benefits of two-factor authentication are simple: it requires a user to consult a source that is not readily available on the computer and is singularly designated in order to gain access to a website or an app. It’s statistically impossible for a hacker to be able to brute force a two-factor authentication system because the second password is randomly generated for every login. Instead of requiring just one step for authentication, such as passwords (which is something you know), it requires two steps. Your ATM card is an example. When you withdraw money from an ATM machine, you are actually using a form of two-step verification. To prove who you are when accessing your money, you need two things: the ATM card (something you have) and the PIN number (something you know). If you lose your ATM card your money is still safe; anyone who finds your card cannot withdraw your money as they do not know your PIN (unless you wrote your PIN on your card, which is a bad idea). The same is true if they only have your PIN and not the card.

Where can it be Used or Applied?
Mostly, Two-factor authentication or Two-Step Verification is used for verifying the authenticity of user’s access to a website or network. It is also used in Banks, e.g. while making transactions both offline and online and you are asked to provide a unique code sent to your phone or from your mobile. It can also be used where ever possible for adequate protection of users, files and system.

Using SMS API for Two-factor/Two-Step Verification.
Any system that makes use of SMS for its verification or authentication makes use of SMS API. SMS API integration enables the SMS to be sent to the user’s mobile phone from the SMS Company’s gateway. Most SMS Marketing Companies have facility for SMPP and HTTP SMS API integration. Your choice of integration depends on what your program is built upon and the users it is meant for. A good web programmer can do this integration.

How much does it cost?
Most companies have free SMS API integration platform or SMS gateway for you to use though you should be aware of those that makes use of the Free Gateway platforms as these delays the sending of SMS to the recipients. A premium SMS gateway services company should be sorted for. Cost will majorly be on the development of the system. However, SMS rate is based on the charge set for outgoing messages.

Where can this Service be gotten?
SMSMarketingPortal.com offers custom design of SMS applications for web and mobile solutions like mobile apps, softwares, web applications, portals, etc with our Free SMS API integration.

Majority of the benefits of two factor / 2 step verification is security. Especially if you want to establish security on a website or admin area of a website.
With the brutal attacks and force hackers are developing nowadays. very soon many site will be implementing it. already big sites like facebook yahoo (mail) and Google are already using this system.

SMS authentiction and API configuring is becomng more popular and can be used in a variety of way including

i. Fighting piracy (book, Movie, etc)
ii. Fighting counterfeit drugs and food (e.g for anti malarial verification)
ii. allowing restricted access to sensitive databases and information (e.g; a Bank account or a mobile app)

And so much more infact the use of sms api can only be left to the imagination as even gamers and IOT (Internet of Things) enthusiasts are now using it for a myriad of solutions.
The use of it can only now be left to one's creative imagination.

For more details about and to learn about this amazing feature and use of sms. Check it out on this blog
http://smsmarketingportal.com/blog/?s=sms+authentication&searchsubmit=Search

or here for a sample summary of one 'tech ecosystem' that can be used

http://www.smsmarketingportal.com/our-services/longcode-sim-hosting

OP you are smart , the underlying objective was to provide your SMS services as a choice, anyway I intend to implement such for a custom CMS am working on, will use your services.

pcguru1:
OP you are smart , the underlying objective was to provide your SMS services as a choice, anyway I intend to implement such for a custom CMS am working on, will use your services.

Great! We eagerly waiting to serve you.