Dear readers of Tecnogalaxy, today we are going to see what the OTP code (One-time password) is for, in the field of cryptography and cybersecurity, a password that is valid only for a single login session or a transaction. For this purpose the OTP is also called a disposable password, the OTP avoids a series of shortcomings associated with the use of the traditional password, in most cases it is received via SMS, sometimes even via e-mail.


Being a momentary password lasting a few seconds becomes very difficult to intercept, the code arriving (in the case of the SMS message), directly on the phone, only those who own it can see it and use it within the set time. The security also rises because the code is automatically made usable after its validation.


The generation of this code (OTP) depends on the user, could be generated by a server and sent via SMS to the applicant, or created through a generator (whether it is a device or an app on your device).


In most cases, the algorithms used to generate an OTP code refer to random numbers.

The OPT code can be generated using the algorithms:

  1. They work according to the time synchronization between the client and the authentication server.
  2. Algorithms in which the password depends on a challenge and a counter.
  3. From algorithms where the new password is generated according to the previous one.


Reliability is undoubtedly higher than other techniques because the password is only available to the user who requests it.

Let’s take an example, when buying an item with payment by credit card, to complete the payment we are required to enter the card details, in case of loss before the card is blocked the scammer can safely use it.

Managing the OTP code, the procedure is different because to complete the payment in addition to the credit card details will be required to also enter the OTP code, which being generated at the moment, as you can imagine without that code we can not do anything.


The use of the OTP via SMS and the sending of temporary passwords may vary depending on the system, but usually implies some fundamental steps:

  1. A user tries to access a protected system
  2. The system generates a temporary password that meets the security requirements deemed necessary, “such as length, use of special characters or punctuation elements”… etc
  3. The OTP code is sent to the user via SMS, to the mobile phone number specified by the user during registration.
  4. The end user receives the OTP code via SMS and inserts it in the appropriate space indicated
  5. The portal verifies the correctness of the temporary password and allows the user to safely access their account;


An OTP code is ultimately a disposable password formed by an alphanumeric code that is automatically generated by special devices, “called in technical jargon token“, or sent to the user via an SMS message, or by email or by using smartphone apps.

All disposable passwords are generated by applying a cryptographic function to a unique set of values, OTP algorithms are quite different from each other to avoid the risk that a cyber criminal can easily predict the future OTP code after analyzing the previous one.

Concluding from how you could understand the OTP code can be counted among the systems with a very high level of security for online operations: thanks to the password generated at the moment and usable within a short time, this system is very secure.

As always make good use of it by making tests on your devices / computers , making them on devices/ computers is illegal.

To the next article!

N.B.: I do not assume any responsibility for the use that you will make of the guide, as drawn up for educational and educational use.

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