![]() ![]() 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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