The discrepancy is averagely 2 minutes per year. But the time the server has is always precise. With no way to sync the time, a drift happens eventually. But the TOTP algorithm relies on the time, so the tokens are supplied with a clock of sorts - an oscillator. This makes it impenetrable for the majority of known hacker attacks. | Read also: 2FA Security Flaws You Should Know AboutĪ TOTP hardware token is completely offline, no network connection whatsoever. But we’ve already solved it in programmable tokens Protectimus Slim NFC. TOTP tokens do have their own issue - time drift. The token button can be clicked as many times as your heart desires, it won’t put the token and server out of sync. So writing the OTPs down won’t do a hacker any good. If a password provided by an RFC6238 TOTP generator is not used within 30, sometimes 60 seconds, it simply expires and can not be used for login. In the HOTP vs TOTP battle, TOTP security would certainly win. The hacker would have to get access to the token and write down a few of the OTPs, the password guessing will take some serious computing and a few hours. HOTP is also more vulnerable to brute-force attacks and other ways to guess the next OTP. This is accounted for in the algorithm, but if someone clicks the button too many times unintentionally (a child plays with it), or intentionally (a criminal) the token is rendered useless. Remember, the counter increases with each new OTP? The server has no ability to follow how many times the token button is clicked since the physical tokens are completely offline. The HOTP passes do not have an expiration time, the hacker just has to use one faster than the owner.Īnother drawback of HOTP is the server-token unsynchronization if the button on the device is pressed too many times. If a HOTP OTP token falls into a hacker’s hands, the criminal can write down the OTPs and use them at any time. HOTP is a lot less bulletproof than the time-based one-time password algorithm. So in 2008 OATH presented TOTP as an expansion of the parent algorithm, the next step of the MFA evolution. The counter-based method has a number of flaws, we’ll touch upon them next. We’ve described this algorithm in every detail in this article. The creation of a one time password is the event for the counter in HOTP, so each new password increases the counter by 1. This method uses a counter as a variable and a seed as a shared value to create OTP. The first algorithm that the organization created is HOTP - HMAC-based One-time Password, presented in 2005. OATH has been actively working on secure 2FA since 2004. This result is what we called a HASH value above. Finally, the mentioned HASH function is a cryptographic mathematic function that simply changes one value into another and usually shortens the result to 6-8 symbols. The timesteps are to be 30 or 60 seconds, so the time value used for TOTP is the number of seconds run since 00:00 January 1, 1970, divided by 30, or 60. The timestep is calculated using UNIX time, which starts on January 1, 1970, UTC. Alternatively, the key is already programmed in their TOTP device. “Sharing” the key usually implies scanning a QR code that shows the seed generated by the server with the client’s TOTP app. To explain the above example a bit let’s note here that the mentioned seed is a string of random characters, usually 16–32 characters long.
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