One-time password (OTP) protocols and implementations (software and hardware)

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97
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3answers
35k views

How does Google Authenticator work?

Google Authenticator is an alternative to SMS for 2Step verification, installing an app on Android where the codes will be sent. It works without any connectivity; it even works on plane mode. This ...
79
votes
6answers
21k views

How secure are the FIDO U2F tokens

Google and Yubico just announced the availability of cryptographic security tokens following the FIDO U2F specification. Is this just another 2FA option, or is this significantly better than solutions ...
16
votes
1answer
1k views

FIDO, U2F Compatibility

I've been following the FIDO standard (a consumer-friendly public-key system similar to SSH key pairs) and it appears that it's close to being complete: both Google and PayPal have been testing it ...
12
votes
1answer
843 views

Why is the truncate function for HMAC one time passwords so complicated?

I've been reading through RFC4226 as part of some research and I was wondering why the function to truncate the HMAC was so complicated. As far as I understand it, the last 4 bits of the HMAC define ...
11
votes
4answers
1k views

What is the use of the “secret” displayed when setting up 2 Factor Authentication?

What is the purpose of the "secret" that is displayed when you take the picture of the QR code to set up 2 Factor Authentication on a non-Google site? Why would you need it? If you save it, doesn't ...
11
votes
3answers
2k views

What is the risk and mitigation of accidentally typing a YubiKey password in an open forum?

I have a YubiKey in my laptop (for testing) and accidentally broadcast my YubiKey password out to the Internet. Since this is only a test key, and has no access to anything of value, here are some ...
10
votes
2answers
3k views

LastPass Grid Authentication vs Google Authenticator which one is more secure?

[Being a LastPass user] recently I moved to Google Authenticator instead of using Grid Authentication as a 2-factor security. For me, finding and filling letters from such a dense matrix is a rather ...
10
votes
1answer
3k views

What are the differences between the U2F and UAF FIDO authentication standards?

Google recently announced support for Universal 2nd Factor (U2F) authentication in Chrome and started allowing that authentication mechanism to be used for 2-factor authentication across their various ...
9
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2answers
2k views

How to store OTP seed securely at the validating server

'Everyone' knows when storing passwords in a database this should be done securely for example by using salts and an appropriate hashing algorithm. Most OTP (One Time Password) solutions are based on ...
8
votes
2answers
950 views

Replacement for One Time Passwords (OTP)

OTP may known as new generation of password security techniques, but I want to know does it still safe enough after several years of appearance or it will deprecate soon? & what would be the ...
8
votes
2answers
195 views

What happens if a (google authenticator) one time password QR code is leaked?

When there are QR codes for one time password (OTPs) urls (starting with otpauth://) that are supposed to be looked up in an authenticator app such as Google authenticator, what happens if a user ...
6
votes
3answers
7k views

Does adding two-factor authentication by OTP really make KeePass more secure

KeePass is an application that keeps all your passwords for you in a database. It is primarily protected by a master password and/or keyfile. If the database is properly encrypted with that password ...
6
votes
1answer
281 views

What's the use of adding a challenge to a one time password algorithm?

In these YouTube videos Challenge-Respond Mode and Sign Mode the customer enters a challenge into the CAP device before generating a one time password. Why not just generate the one time password ...
6
votes
1answer
360 views

Why does my bank bother asking basic personal questions to log in to online banking?

To log into my online banking, I have to answer a basic personal question such as "What is your mother's maiden name" or "What is your grandfather's middle name", as well as enter a one-time code from ...
5
votes
2answers
926 views

HOTP with as HMAC hashing algoritme a hash from the SHA-2 family

I'm looking into using a OTP solution. HOTP is a OTP solution that is based on a HMAC with as hashing algorithm SHA-1. The standards defines it this way. But... SHA1 (as we know) has been a ...
5
votes
2answers
347 views

How secure is a password app that stores both the password and two factor secret in one place?

Take for example 1Password, that now can store your password and one time password secret in a single place (your 1Password vault). I know it isn't truly two-factor anymore, but how much better is it ...
4
votes
2answers
1k views

Is OATH TOTP and / or Google Authenticator vulnerable if an attacker has (N) previous codes?

I'm not much of a ipsec initiate, so this is a bit over my head ... but I'm always willing to learn more. Are there any known attacks against OATH TOTP (Google Authenticator's / Authy's algorithm) if ...
4
votes
4answers
2k views

SMS Authentication: random OTP or a cryptographic one

I'm adding two-factor authentication using SMS to enhance an existing login process. Since I'm not working with physical tokens, I was wondering what is considered the safest: Sending random 8 ...
4
votes
2answers
202 views

Email for the second factor in 2FA systems

the scenario is in a corporate environment and not connected to internet. The other day I was arguing with my colleague on whether email is good enough to be the second factor in a 2FA system. My ...
4
votes
1answer
117 views

One time password question

Suppose F(X) = (5X) mod 9 is used to generate a one time password. I am supposed to generate the first 8 values using the above formula, starting with the seed value of F(5) Well I know that F(5) = ...
4
votes
4answers
2k views

One Time Password via Text Message: Possible exploits?

Is there a credible scenario in which the OTP (One Time Password) for online credit card transactions ( specifically for Verified by Visa) can be bypassed? Context: A guy I know was cheated via the ...
4
votes
1answer
222 views

Google Authenticator Error on Reboot

I have set up an SSH server to accept only login using codes generated by Google Authenticator (I have disabled all other forms of authentication on that port). After having rebooted my remote ...
4
votes
1answer
1k views

How do OTP USB sticks work?

I just discovered the YubiKey NEO which seems like a pretty awesome device for maintaining security for a variety of different things including computer login, SSH private keys, GPG private keys, and ...
3
votes
1answer
48 views

Is symmetric encryption with one time pre-shared key secure?

Suppose I have a secure channel between client and server, with proper certificate validation etc (actually, ssh session). I want to establish a secure connection between my own application on a ...
3
votes
4answers
168 views

Are there any two way + two factor authentication systems in use?

My bank, Google etc. use two factor systems where they send me a One Time Password via out of band means. e.g. SMS or an App on my Cellphone or a standalone RSA token generator. This seems good ...
3
votes
1answer
3k views

Please explain Time-step in Time-Based One-Time Password Algorithm

I am studying about OTPs (One Time Passwords). I have gone through all the methods: HOTP (HMAC-based One Time Password), TOTP (Time-based One Time Password) I have no issues with HOTP. But according ...
3
votes
3answers
2k views

Mobile OTP - Secure?

I came across Mobile-OTP, "a de facto standard for strong mobile authentication" (http://motp.sourceforge.net). The developers claim that it is very secure etc. Reading through the implementation, I ...
3
votes
2answers
1k views

Is HMAC-SHA256 and HMAC-SHA512 able to act as drop in replacement for HMAC-SHA1 in HOTP/TOTP?

In RFC 4226, the algorithm for HOTP is described as follow. HOTP(K,C) = Truncate(HMAC-SHA-1(K,C)) TOTP is essentially the same algorithm as HOTP except for the fact that the counter C is ...
3
votes
1answer
133 views

Should an administrator be able to turn off TFA for a user

We use Google Authenticator and SMS for two factor authentication. Should we allow the administrators of the site to turn off TFA for users? Google Auth uses SMS as backup option but SMS does not ...
3
votes
1answer
194 views

S/Key as an alternative to UNIX passwords

There is this password system called S/Key I saw on the Internet. Can someone give me a brief description about S/Key and how it works? Can S/Key be an alternative solution to the UNIX password ...
3
votes
1answer
976 views

Is Dual Factor possible during boot with whole disk encryption on Mac FileVault 2

Mac FileVault 2 is the default disk encryption for newer Macs that occurs in the EFI pre-boot phase. The challenge here is that most smartcard drivers are loaded after the OS loads. Is anyone aware ...
3
votes
3answers
262 views

Should LastPass use the YubiKey public identifier as a secret key?

I've just picked up a YubiKey. However, the demo Yubico redirect you to is served over plain HTTP, over which each OTP you generate during the demo is POSTed, enabling you to verify that your key is ...
3
votes
1answer
50 views

Relative merits of Yubico OTP vs. OATH-HOTP?

What are the pros and cons of using Yubico OTP vs. OATH-HOTP? They both seem very similar.
3
votes
1answer
79 views

Using the password, among other values, as key data in two-factor authentication

I'm writing an implementation and a thesis about two-factor authentication, and am currently doing some research. I'm currently looking at an implementation for deterministically generating a ...
3
votes
2answers
1k views

Security evaluation of Vasco's Digipass Mobile SDK for OTP?

Has anybody worked with or integrated the Vasco Digipass Mobile SDK OTP generator into a custom mobile app for iOS devices? I am currently performing a full security evaluation of the solution ...
3
votes
0answers
127 views

How is PasswordSafe different from KeePass/OtpKeyProv?

Over at Does adding two-factor authentication by OTP really make KeePass more secure the top answer unmistakably states that KeePass is not made more secure by using an OTP. I told a friend I was ...
2
votes
2answers
55 views

Is email OTP improving the security for 2 phase authentication?

There has been similar questions before where people say that using some other means (sms, hardware devices, etc.) is a more secure way to provide 2 factor authentication. Provided we don't have an ...
2
votes
3answers
1k views

What are the main weaknesses of mobile software based OTP generators?

What are the main weaknesses of Software based OTP generators like Vasco's DigiPass for Mobile?
2
votes
3answers
291 views

Why would it be a good idea for someone to get or not to get a Yubi key [closed]

In what uses would it be smart to get a Yubi key?
2
votes
4answers
1k views

One-Time-Passwords resist against bruteforce attacks? Immune Alternative?

Does a One-Time-Password like Google Authenticator or YubiKey protect against brute force attacks with unlimited computer power? If not, what algorithems are immune to bruteforce attacks against ...
2
votes
2answers
305 views

Client code tampering detection

I have a server in a trusted environment. This server handles requests from clients in an a non-trusted environment. I'd like to authenticate each request and to know if the client code has been ...
2
votes
1answer
567 views

Are there any secure ways to store the secret key used in a TOTP scheme?

I'm writing a little webapp that demonstrates 2 factor authentication. I'm using the TOTP protocol as described in RFC 6238. In our scheme, we are storing, in addition to a b-crypted password hash ...
2
votes
1answer
54 views

Security implications of reusing unused One-Time Password

Scenario: Login to site (using 2SV). One-Time Password (OTP) is sent to client's device. Client won't finish authentication process. On the next day (let's say after 24h) users logins to site again. ...
2
votes
1answer
181 views

Lamport OTP system

This might be a stupid question but forgive me. Is the Lamport OTP algorithm different from HOTP and TOTP? How similar or different are they? Thanks in advance
2
votes
2answers
2k views

How to write a rock solid TOTP implementation?

I am currently writing a TOTP implementation in PHP (but this applies to other languages as well) and of course want it to be as secure as possible, what should be considered? After reading the ...
2
votes
2answers
90 views

HOTP/similar - how about standard backups of mobile devices?

I was considering adding HOTP as an option to my website (alongside things such as SMSed one time tokens which I already have). But I was considering one issue that HOTP inherently has: Things such ...
2
votes
1answer
747 views

What is more secure for voice and SMS OTP: A random number or generated similar to HOTP?

Many providers are creating OTP authentication for their sign in. However I noticed that all the voice and SMS OTPs I've come across are a series of 6 digits... similar to the HOTP RFC Standard ...
2
votes
1answer
102 views

OTP on the same device being used to login

I've seen mobile apps use two factor authentication by sending an SMS to the mobile phone. However, if I've stolen someone's phone, where is the security advantage? I can understand it if it's used in ...
2
votes
2answers
205 views

TOTP Resynchronisation

Considering hardware tokens implementing OATH TOTP (c.f. RFC6238), it is common knowledge that the clock in such tokens drift. A token that is not used very often is likely to drift way beyond the ...
2
votes
1answer
97 views

What happens when authenticating through a phishing attack with FIDO U2F tokens

So I have looked around and haven't found this anywhere. What happens when the response server is a phishing site with FIDO U2F tokens? Basically, if login just fails, I would assume that the user ...