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Last year I got the Google Titan security keys and connected it with all of my work + personal accounts that support it. The #1 weakness is the simple fact tha

by cj 7y ago

Last year I got the Google Titan security keys and connected it with all of my work + personal accounts that support it. The #1 weakness is the simple fact that many services don't allow you to disable alternate forms of 2fa. Github is an example, you can always trigger the fallback SMS 2fa code. Dashlane is another example (and arguably the most important). It's impossible to make your security key the only form of 2-FA. If you have a security key on your account, you must also have regular app-based 2-FA enabled as a fall back. What's the point of using security keys with services that require regular SMS or app-based 2-FA as a fallback? Edit: G Suite is one of the few services that got it right. G Suite has an optional security control that when enabled, forces authentication using security keys (explicitly forbidding alternate 2-fa methods).

somepig 7y ago
regular "app based" is just OATH-TOTP in most cases. This uses a shared secret and the time to generate one time codes. The Yubikey explicitly supports TOTP, and will happily store your secret on the key. You can then use Yubioath to pull codes from the Yubikey as needed. I'm a huge fan of the ability to use either U2F or TOTP with the same hardware token.
- mfontani 7y ago
  Note that the Yubikey only supports up to 32 TOTP.
Macha 7y ago
My understanding is the issues that lead to U2F being considered to be better than TOTP were mainly about it being phished easily compared something which will only dispense the right code with the right challenge. But if you never actually login with TOTP, and always use your U2F key, then does it actually decrease security to have it as a backup/removal option and you know that's the only reason you'd enter it. It feels like its competition there is "convince phone support with a sob story" and TOTP feels like a clear step up from that.
- antsar 7y ago
  TOTP is one thing. Having your backup TOTP key locked in a safe effectively stops it from being abused. SMS 2FA, on the other hand, has real security issues[0][1]. In my experience, SMS 2FA is most commonly the required type of 2FA, before you can add TOTP/U2F as a secondary. SMS 2FA is the hardest to lose or break, so forcing everyone to keep it enabled minimizes support costs for the provider. [0] https://www.theregister.co.uk/2016/07/24/nist_says_sms_no_good_for_authentication https://www.theregister.co.uk/2016/07/24/nist_says_sms_no_go... [1] https://duo.com/decipher/reddit-breach-illustrates-dangers-of-2fa-over-sms https://duo.com/decipher/reddit-breach-illustrates-dangers-o...
  - yborg 7y ago
    The other thing driving SMS 2FA is that this is a clean way for the site/org to get their hands on a real phone number for you with no extra effort. SMS 2FA has been repeatedly proven to be trivial to break with a simple phone call to a mobile provider, since there so far is no downside at all that I am aware of to the providers. If someone jacks your SMS and drains your bank account, at least in the US your mobile provider just goes "oops". Until there is some penalty for them allowing your number to be ported without your consent, SMS is essentially useless for real 2FA security. Even if the account security was foolproof, though, it still is vulnerable to SS7 routing attacks.
  - srathi 7y ago
    Using Authy may be a good idea. There is a slight risk of exposing the TOTP key to the cloud, but having it available on all devices (current and future) is very convenient. Authy has an option to encrypt the key using a user specified passphrase, so it is at least better than storing the raw TOTP key in the cloud.
- tialaramex 7y ago
  There's a small downside to TOTP even if you never use it in anger. For U2F/ WebAuthn the relying party doesn't end up knowing any secrets. So if for example I get a month old database backup of Facebook, I don't learn how to log in with U2F as any of the users whose credentials I have, because Facebook can't do that either, only the legitimate users can. For TOTP that stolen data gets me in, because I can synthesize correct TOTP codes for any user whose secret key I have stolen. But you are correct that social engineering attacks will be far more common. The particular concern with SMS is that the attack can target your mobile phone company, so that all the security at say Facebook or Twitter doesn't help you because your security was blown up at T-mobile or AT&T.
jxcl 7y ago
Fastmail allows you to do this too. They have a long section in the documentation that strongly discourages it, and it seems like they will refuse to restore your account if you lose your 2FA, which is exactly what I want: https://www.fastmail.com/help/account/2fa.html https://www.fastmail.com/help/account/2fa.html >> Why do I have to add a recovery phone number to set up two-step verification? > Keeping your account safe from attackers is very important. But so too is making sure you don't get locked out of your own account. We are aware that SMS is not the most secure of methods for 2FA, and has been deprecated by NIST. However, for the majority of users, the risk of losing their two-step verification device is far greater than the risk of someone hacking their SMS. If you lose your phone, the TOTP key is lost but normally you can get a new SIM card with the same number from your carrier. We therefore believe requiring a phone as a backup option strikes the best balance of confidentiality (no one else can read your data) and availability (you can read your data) for the majority of our users. > Please note, if two-step verification is enabled, access to the phone number itself is not sufficient to gain access to an account: you still need two factors (your password AND the SMS). > Advanced users that understand the risk may remove the phone number from their account once two-step verification is enabled. Once the recovery phone is removed from the account, SMS is no longer an option as the second factor for login. If you choose to do this, we strongly recommend you write down or print your recovery code and store it in a safe location, and that you set up at least two security keys or authenticator devices. Should you lose access to all two-step verification devices and not have your recovery code, you may be permanently locked out of your own account.
- alasarmas 7y ago
  Fastmail used to have a mechanism where you could hold down <alt> (I believe) on that screen and phone number would no longer be a required field to continue creating your account. Maybe that's still possible.
  - jxcl 7y ago
    I don't remember phone number being required while creating an account, they only wanted to collect it when enabling 2FA. If I recall correctly they had a little info button that said something like "we need this to start but you can remove it later if you _really_ want to."
ecesena 7y ago
> Github is an example, you can always trigger the fallback SMS 2fa code. You can setup OTP (no SMS) and either keep it as a backup, or destroy the key. I don't have SMS on Github. Admittedly, it won't solve issues with all services. From the service perspective, dealing with users who lost their security key (or don't have a backup one) is too painful wrt to forcing you to have an alternative.
apex3stoker 7y ago
> What's the point of using security keys with services that require regular SMS or app-based 2-FA as a fallback? It addresses the problem with phishing. The main problem with Authenticator is not that an attacker knows the one-time password, but that an attacker tricks user into entering the one-time password to their UI and uses that right away to take control of the user's account. https://krebsonsecurity.com/2018/07/google-security-keys-neutralized-employee-phishing/ https://krebsonsecurity.com/2018/07/google-security-keys-neu...
zymhan 7y ago
Dashlane's support isn't an issue IMO. TOTP is secure, unlike SMS 2FA.

by cj 7y ago

somepig 7y ago

regular "app based" is just OATH-TOTP in most cases. This uses a shared secret and the time to generate one time codes. The Yubikey explicitly supports TOTP, and will happily store your secret on the key. You can then use Yubioath to pull codes from the Yubikey as needed. I'm a huge fan of the ability to use either U2F or TOTP with the same hardware token.

mfontani 7y ago
Note that the Yubikey only supports up to 32 TOTP.

Macha 7y ago

My understanding is the issues that lead to U2F being considered to be better than TOTP were mainly about it being phished easily compared something which will only dispense the right code with the right challenge. But if you never actually login with TOTP, and always use your U2F key, then does it actually decrease security to have it as a backup/removal option and you know that's the only reason you'd enter it. It feels like its competition there is "convince phone support with a sob story" and TOTP feels like a clear step up from that.

antsar 7y ago
TOTP is one thing. Having your backup TOTP key locked in a safe effectively stops it from being abused. SMS 2FA, on the other hand, has real security issues[0][1]. In my experience, SMS 2FA is most commonly the required type of 2FA, before you can add TOTP/U2F as a secondary. SMS 2FA is the hardest to lose or break, so forcing everyone to keep it enabled minimizes support costs for the provider. [0] https://www.theregister.co.uk/2016/07/24/nist_says_sms_no_good_for_authentication https://www.theregister.co.uk/2016/07/24/nist_says_sms_no_go... [1] https://duo.com/decipher/reddit-breach-illustrates-dangers-of-2fa-over-sms https://duo.com/decipher/reddit-breach-illustrates-dangers-o...
- yborg 7y ago
  The other thing driving SMS 2FA is that this is a clean way for the site/org to get their hands on a real phone number for you with no extra effort. SMS 2FA has been repeatedly proven to be trivial to break with a simple phone call to a mobile provider, since there so far is no downside at all that I am aware of to the providers. If someone jacks your SMS and drains your bank account, at least in the US your mobile provider just goes "oops". Until there is some penalty for them allowing your number to be ported without your consent, SMS is essentially useless for real 2FA security. Even if the account security was foolproof, though, it still is vulnerable to SS7 routing attacks.
- srathi 7y ago
  Using Authy may be a good idea. There is a slight risk of exposing the TOTP key to the cloud, but having it available on all devices (current and future) is very convenient. Authy has an option to encrypt the key using a user specified passphrase, so it is at least better than storing the raw TOTP key in the cloud.
tialaramex 7y ago
There's a small downside to TOTP even if you never use it in anger. For U2F/ WebAuthn the relying party doesn't end up knowing any secrets. So if for example I get a month old database backup of Facebook, I don't learn how to log in with U2F as any of the users whose credentials I have, because Facebook can't do that either, only the legitimate users can. For TOTP that stolen data gets me in, because I can synthesize correct TOTP codes for any user whose secret key I have stolen. But you are correct that social engineering attacks will be far more common. The particular concern with SMS is that the attack can target your mobile phone company, so that all the security at say Facebook or Twitter doesn't help you because your security was blown up at T-mobile or AT&T.

jxcl 7y ago

Fastmail allows you to do this too. They have a long section in the documentation that strongly discourages it, and it seems like they will refuse to restore your account if you lose your 2FA, which is exactly what I want: https://www.fastmail.com/help/account/2fa.html https://www.fastmail.com/help/account/2fa.html >> Why do I have to add a recovery phone number to set up two-step verification? > Keeping your account safe from attackers is very important. But so too is making sure you don't get locked out of your own account. We are aware that SMS is not the most secure of methods for 2FA, and has been deprecated by NIST. However, for the majority of users, the risk of losing their two-step verification device is far greater than the risk of someone hacking their SMS. If you lose your phone, the TOTP key is lost but normally you can get a new SIM card with the same number from your carrier. We therefore believe requiring a phone as a backup option strikes the best balance of confidentiality (no one else can read your data) and availability (you can read your data) for the majority of our users. > Please note, if two-step verification is enabled, access to the phone number itself is not sufficient to gain access to an account: you still need two factors (your password AND the SMS). > Advanced users that understand the risk may remove the phone number from their account once two-step verification is enabled. Once the recovery phone is removed from the account, SMS is no longer an option as the second factor for login. If you choose to do this, we strongly recommend you write down or print your recovery code and store it in a safe location, and that you set up at least two security keys or authenticator devices. Should you lose access to all two-step verification devices and not have your recovery code, you may be permanently locked out of your own account.

alasarmas 7y ago
Fastmail used to have a mechanism where you could hold down <alt> (I believe) on that screen and phone number would no longer be a required field to continue creating your account. Maybe that's still possible.
- jxcl 7y ago
  I don't remember phone number being required while creating an account, they only wanted to collect it when enabling 2FA. If I recall correctly they had a little info button that said something like "we need this to start but you can remove it later if you _really_ want to."

ecesena 7y ago

> Github is an example, you can always trigger the fallback SMS 2fa code. You can setup OTP (no SMS) and either keep it as a backup, or destroy the key. I don't have SMS on Github. Admittedly, it won't solve issues with all services. From the service perspective, dealing with users who lost their security key (or don't have a backup one) is too painful wrt to forcing you to have an alternative.

apex3stoker 7y ago

> What's the point of using security keys with services that require regular SMS or app-based 2-FA as a fallback? It addresses the problem with phishing. The main problem with Authenticator is not that an attacker knows the one-time password, but that an attacker tricks user into entering the one-time password to their UI and uses that right away to take control of the user's account. https://krebsonsecurity.com/2018/07/google-security-keys-neutralized-employee-phishing/ https://krebsonsecurity.com/2018/07/google-security-keys-neu...

zymhan 7y ago

Dashlane's support isn't an issue IMO. TOTP is secure, unlike SMS 2FA.