TOTP authentication with free software [LWN.net]
One-time passwords (OTPs) are increasingly used as a defense against phishing and other password-stealing attacks, usually as a part of a two-factor authentication process. Perhaps the most commonly used technique is sending a numeric code to a phone via SMS, but SMS OTPs have security problems of their own. An alternative is to use time-based one-time passwords (TOTPs). The normal TOTP situation is to have all of the data locked into a proprietary phone app, but it need not be that way.