YubiKey 4 Nano This is an OLD PRODUCT. There is a newer product available, the YubiKey 5 Nano - now available on Amazon :: http://www.amazon.com/dp/B07HBDX2CM Two-factor authentication made easy for hundreds of services - USB Type A compatible Smart card (PIV), Yubico OTP, OATH-TOTP, OATH-HOTP, FIDO U2F, OpenPGP, Challenge-Response Use as standalone security key or attach string lanyard Extremely durable and rigid; crush and water resistant - Not for keychains or key rings Strong two-factor hardware based authentication Easy and fast authentication with a single touch Reduces IT operational costs Multi-protocol support on a single key Crush-resistant and waterproof Made in the USA Supported protocols: FIDO U2F, smart card (PIV), Yubico OTP, OpenPGP, OATH-TOTP, OATH-HOTP, and Challenge-Response Secure element hardware to protect cryptographic keys Crypto Algorithms: RSA 2048, ECC p256, ECC p384 Interface: USB-A Works on Microsoft Windows, Mac OS X, Linux, Chrome OS operating systems, and on major browsers Now works with Twitter! PIV smart card compatible, minidriver available on Windows Support for PKCS#1