As of 2003, RSA SecurID commanded over 70% of the two-factor authentication market[REF] and 25 million devices have been produced to date.
Other network authentication systems, such as OPIE and S/Key (sometimes more generally known as OTP, as S/Key is a trademark of Telcordia Technologies, formerly Bellcore) attempt to provide the "something you have" level of authentication without requiring a hardware token.