The Yubikey 4 also provide more functionality such as PGP. This is more like the Yubikey Security Key ($20): https://www.yubico.com/product/security-key-by-yub

The Yubikey 4 also provide more functionality such as PGP. This is more like the Yubikey Security Key ($20): https://www.yubico.com/product/security-key-by-yubico/#security-key https://www.yubico.com/product/security-key-by-yubico/#secur...