One-Time Passwords: A Literary Review of Different Protocols and Their Applications

Currently, user authentication only based on passwords can be inadequate due to different types of vulnerabilities and attacks. To solve this problem, two-factor authentication is commonly used, providing a higher level of security when the user logs into their accounts, and one popular example of two-factor authentication is the combination of password and One-Time Passwords (OTP). Due to the importance and popularity of OTPs, this study analyzed the most widely used OTP protocols and their applications to understand their state of the art. The scientific community can use the analysis carried out in this work to understand why OTP is so popular and to decide on the type of OTP, in case a custom implementation is needed for an authentication system. To achieve this, this work analyzed a large number of previous works methodically through a semi cyclic process based on research action combined with a systematic review process. The most important works were analyzed to identify their specific features and to classify the used technologies. Usage trends in terms of protocols, implementations, algorithms, and OTP generators were also analyzed. In addi-tion, this article has determined a complementary feature guide that must be considered when implementing an OTP authentication system.