<P> Although OTPs are in some ways more secure than a static memorized password, users of OTP systems are still vulnerable to man - in - the - middle attacks . OTPs should therefore not be disclosed to any third parties, and using an OTP as one layer in layered security is safer than using OTP alone; one way to implement layered security is to use an OTP in combination with a password that is memorized by the user (and never transmitted to the user, as OTPs often are). An advantage to using layered security is that a single sign - on combined with one master password or password manager becomes safer than using only 1 layer of security during the sign - on, and thus the inconvenience of password fatigue is avoided if one usually has long sessions with many passwords that would need to be entered mid-session (to open different documents, websites, and applications); however, the disadvantage of using many forms of security all at once during a single sign - on is that one has the inconvenience of more security precautions during every login--even if one is logging in only for a brief usage of the computer to access information or an application that doesn't require as much security as some other top - secret items that computer is used for . See also Related technologies, below . </P> <P> More often than not, one - time passwords are an embodiment of two - factor authentication (2FA or T - FA). 2FA is a form of layered security where it is unlikely that both layers would be compromised by someone using only one type of attack . </P> <P> Some single sign - on solutions make use of one - time passwords . </P> <P> One - time password technology is often used with a security token . </P>

How many different documents can open at one time