Cassie is considering the use of password key devices for her company and wants an open standard for authentication that is widely recognized. She also requires her keys to be compatible with USB, Bluetooth, and NFC connections. Which standard should she seek for her keys to implement?

Among the choices given, FIDO U2F, which is an open standard established by the Fast IDentity Online Alliance, is the only standard specifically for security keys. Other standards that may come up include OTP (One Time Password), SmartCard, OATH-HOTP, and OpenPGP. It's worth mentioning that OATH, the Initiative for Open Authentication, provides standards for both HMAC-based one-time password (HOTP) and TOTP (time-based one-time passwords). SAML (Security Assertion Markup Language) and OpenID are both utilized in authentication procedures but not for security keys. ARF is a fabricated acronym for this question.