Single-Factor Authentication (SFA) is the classic and most commonly used authentication method for secure access to a system, network or website. The user
who wants to establish access only needs a single credential. In addition to single-factor authentication, there is two-factor authentication (2FA), which uses two factors, and multifactor authentication (MFA), which uses three factors. As for Single-Factor Authentication, it relies on terms that the user knows well. For example, the username and a password are combined. These authentication factors are called Knowledge Factors because only the user can know them. Knowledge-Based Authent
ication(KBA) is another method that requires the user to answer a personal question, and
can make Single-Factor Authentication (SFA) a secure authentication method.These authentication factors are called inherence factors because they are immutable characteristics of the user.
The security achieved by the SFA method also results from the care with which the characteristic is selected. If a higher level of security is required, then this can be achieved by the methods with two or more factors.