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Passkeys will come at a cost

fy.blackhats.net.au

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Re: Passkeys will come at a cost

#111

Post by kj4ips »

a-dub wrote: post #59

this is probably a dumb question, but why not just store a secret seed that is used with an on device prng to generate as many secrets as you need where a sequence id gets shared with the counterparty?

I'm pretty sure that is how non-resident keys work on some platforms (like the first gen yubico U2F tokens).

The main feature of resident (aka discoverable) keys is that the RP doesn't need to know anything about which key is about to be used, so it can just say "send me an auth for example.com", and the browser and key handle the rest.

However, with non-discoverable keys, the RP has to provide a reference to the key, which could actually have encrypted private key matter in it.

Re: Passkeys will come at a cost

#112

Post by pndy »

asdff wrote: post #37

Passkeys make no sense. Its selling you something you already own, since a fingerprint or a retina scan makes a fine good two factor as well.

> since a fingerprint or a retina scan makes a fine good two factor as well

Last year I was making new IDs for myself and my mother which in the newest version require fingerprints being provided beside the biometric photo. The office clerk lady who served us had a real struggle with taking scans of our fingerprints. Our skin was damaged due to low temperature and extensive use of alcohol-based sanitizing gel because of the current situation back then. She gave us vaseline cream so this would go a little bit easier but no luck - each of us spent around 10 minutes scanning each finger till it got finally digitalized.

The scanner used could a really cheap one and thus blamed for prolonging this whole scanning process or it was our skin condition or both these things. Whether it was, by this experience even if episodic one, I don't think that fingerprints are "a fine two factor".

As for eyes: it's really unlikely it might happen to many people but eyes can be damaged and there are eye diseases that might affect verification. Not mention post-procedures treatment that excludes use of this scan technique for some time.

Re: Passkeys will come at a cost

#113

Post by wepple »

> Are non-resident keys less secure?

The answer provided by the author (TLDR: you'd have to break AES) is far from satisfying to me.

With a resident key, the only thing an attacker on an endpoint could ever get is a challenge & a response to that challenge. It's more than nothing, but limits a lot of attacks.

With non-resident keys, an attacker can not only do all kinds of offline attacks* against the HMAC and crypto, but also has a far better position of attack against the the security key: you've got decryption, HMAC, key parsing code all happening on untrusted data (if done correct, HMAC will have to fall first).

Further, you've got twice the encryption happening on the key, which could provide a larger attack surface for side channel attacks.

I'm not saying any of these are trivial or even feasible, just that "citation needed" for resident key == non-resident key, in terms of security.

*if your idea of an offline attack of this nature is "break AES with a brute force" and that's about it, there's a lot more options

Re: Passkeys will come at a cost

#114

Post by kj4ips »

wepple wrote: post #107
a-dub wrote: post #59

this is probably a dumb question, but why not just store a secret seed that is used with an on device prng to generate as many secrets as you need where a sequence id gets shared with the counterparty?

how does authn happen here? RP sends ID and I respond with the secret code? that's subject to replay attacks.

It's a challenge-response with nonces. There is also the browser's role to ensure that a given RP's requests are marked with the origin (domain) they came from, so auth.example.com and auth.example.evil don't overlap. (U2F is mostly concerned about malicious sites, and less about malicious browsers and other nastyware)

Re: Passkeys will come at a cost

#115

Post by taeric »

ericjmorey wrote: post #93
taeric wrote: post #61

Earlier quoted context omitted.

But if the passkeys are copyable off of where you are storing them, then I'm not entirely clear on how they truly up the security? I mean, I get the obvious ways that a challenge system is better than a bearer token. But I feel a ton is lost as soon as you move to the exportable keys. Love to see an exploration on these topics. I confess I have not been following them much, lately.

I think the general idea is that the vast majority of people have a smart phone, so the security model is to let people use the phone as the "key" to access services and take advantage of the biometrics/pin security as the main component of security access. This means that there are a lot of security compromises that make sense in the name of ease of use. This model has been tested to some extent with Apple pay and G…

Oddly, pay/wallet work for completely other reasons. Largely in the absurd amount of monitoring that the credit companies do to watch your transactions. That and the general legal framework around charges.

Consider, that is largely replacing 20ish numbers with something else. Is slightly more convenient for folks, as you have your phone with you a lot.

So, for the passkeys, I know that there is a secure enclave in phones. I was not aware that they could store resident keys. Know what the limits are, there?

Re: Passkeys will come at a cost

#116

Post by JohnFen »

mrtksn wrote: post #84
Ajedi32 wrote: post #27

Is it even a good idea to use physical security keys as passkeys in the first place? Passkeys are meant to be a password _replacement_, and for that you probably want the 2-factor properties afforded by phones or desktops which usually require "something you know" or "something you are" to unlock in addition to the "something you have" afforded by physically possessing them. IMO physical security keys are better left…

If you think about it, the core problem can be described as "authentication of the biological being with an electronic system". When passwords are used, the authentication interface is a keyboard and you don't have any actual guarantees that the person typing the password is the person who claims to be. The passwords could have been extracted in so many ways because it depends on easily transferable knowledge. Moving…

> it's probably illegal and if the bank finds out about it, they will cancel the card.

In the US, anyway, this isn't illegal unless you have to sign something and sign someone else's name. So just sign your own (nobody actually checks signatures).

It might be against the CC issuer's terms of service, of course, but that's a whole lot different from being illegal.

Re: Passkeys will come at a cost

#118

Post by JohnFen »

jauntywundrkind wrote: post #106
the_snooze wrote: post #33

Earlier quoted context omitted.

When I use a Yubikey for passwordless authentication (FIDO2), it challenges me for a PIN before asking me to touch the device. If I give it too many incorrect PINs, the Yubikey locks up and requires a device reset, which invalidates all previous registrations to use that key for authentication. It doesn't seem like a big deal if someone steals my hardware token. https://support.yubico.com/hc/en-us/articles/4402836718…

It means though that your secure hardware token has a reliable way where the secrets all self-destruct. That someone can easily do if they get even brief hardware access. For people who have a problem keeping sufficient backups (almost everyone on earth) this seems like a horrific blocker, a show stopper for this entire intiative. I personally think these things absolutely should be able to be exported & backed up se…

> I personally think these things absolutely should be able to be exported & backed up separately.

I agree. The usual response is that you don't need to do this because you can have multiple hardware keys that authenticate to the same services, so you can store one as a backup.

But managing that sounds like a real pain in the butt to me (honestly, the entire passkey system sounds like a real pain in the butt to me -- but that bit particularly so).

But it looks like the major companies recognize that this is an issue and won't be requiring that part.

Re: Passkeys will come at a cost

#119

Post by ryandrake »

mrtksn wrote: post #84
Ajedi32 wrote: post #27

Is it even a good idea to use physical security keys as passkeys in the first place? Passkeys are meant to be a password _replacement_, and for that you probably want the 2-factor properties afforded by phones or desktops which usually require "something you know" or "something you are" to unlock in addition to the "something you have" afforded by physically possessing them. IMO physical security keys are better left…

If you think about it, the core problem can be described as "authentication of the biological being with an electronic system". When passwords are used, the authentication interface is a keyboard and you don't have any actual guarantees that the person typing the password is the person who claims to be. The passwords could have been extracted in so many ways because it depends on easily transferable knowledge. Moving…

> IMHO, the IT systems desperately need to approach human behaviour by working in analogous ways with the real world. Since I'm involved with IT systems I don't struggle most of the time but people who are not that tech savvy are having hard time figuring out daily stuff

I'm pretty much the website key master for everyone in my family. Since nobody else is "in computers" they really don't have a clue about what things need passwords and why. They would NEVER voluntarily complicate their lives with 2FA or even with a password manager. If it wasn't for me, they'd just use "hunter2" and share it across every single device and service they use. If I told them they couldn't just type in their Netflix password when Gmail was asking for a password, they would just look at me exasperated, like I was making their lives difficult.

The security community really needs to get a grip and start designing systems that are compatible with the extremely low-tech-interest population if we even have a hope of securing systems. If I knew what the solution was I'd be rich.

Re: Passkeys will come at a cost

#120

Post by somehnguy »

saulrh wrote: post #2

That's a rather uncharitable take on the situation. I'll propose an alternative: If you want to take advantage of the new auth standard that will eliminate weak passwords and password reuse (thereby preventing 99% of casual account break-ins), you'll have to spend $30 to upgrade off the legacy yubikey you've been coasting on since 2013.

Someone using easy to guess simple passwords probably isn’t using a Yubikey and also likely has no interest in getting one at all. Those 2 categories are very different people.
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