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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

#161

Post by torstenvl »

I'm not a security or crypto guy at all. I found this very difficult to follow, and I suspect others might too.

My questions probably seem weird to someone with enough background context to understand the post, but I am getting wrapped around the axle every sentence or two.

> It all comes down to one thing - resident keys.

How/why? What's the connection to passkeys or HSMs?

> we need to understand what a discoverable/resident key is

Yeah okay... does this imply that all resident keys are discoverable keys? Or that all discoverable keys are resident keys? Or both?

> You have probably seen that most keys support an 'unlimited' number of accounts.

No. Does "keys" here mean passkeys? Or keys stored on HSMs? Or both? Or something else entirely?

> This is achieved by sending a "key wrapped key" to the security key.

Okay so an HSM can apply to an unlimited number of accounts because it can store... some kind of key wrapped in another key (of the same type? different type?)

Re: Passkeys will come at a cost

#162

Post by pohuing »

0cf8612b2e1e wrote: post #35
dathinab wrote: post #26

Earlier quoted context omitted.

I would go as far and say it's a too charitable take. Shared residual keys _should not exist_ (outside of short term temporary usage, e.g. not 2FA/FIDO). They are a liability, they are a security risk, they promote bad security practices. Best example TOTP (which from a security POV is quite flawed). You don't want to ever share the shared secret across devices (or back it up) but due to it being possible and flawed…

> You don't want to ever share the shared secret across devices (or back it up) Hard disagree there. I do not feel comfortable unless I can backup a key. Phones get lost/broken/stolen all the time. Is it less theoretically secure? Sure, whatever, but I am not James Bond.

That's what the one time use backup keys are for

Re: Passkeys will come at a cost

#163

Post by 8organicbits »

superkuh wrote: post #94

HTTPS only like this blackhats.net.au site comes at a cost too. If there's a browser/server SSL mismatch the text becomes completely unavailable. While if it was an HTTP+HTTPS site I could simply visit the HTTP endpoint. Instead to protect against hypothetical downgrade attacks they've made their content inaccessible and effectively DoS themselves for a small fraction of visitors.

> small fraction of visitors

This site won't work on Windows 7 / Chrome 69 as it only supports TLS 1.3 [1]. I believe 5% of the web can't connect [2].

But the text on the site is for technically minded people and the content includes commands you should run and security configuration. Tampering of the content could be quite harmful.

[1] https://www.ssllabs.com/ssltest/analyze.html?d=fy.blackhats....

[2] https://caniuse.com/?search=tls1.3

Re: Passkeys will come at a cost

#164

Post by secabeen »

Nadya wrote: post #89
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.

What's your game plan for replacing your retina or fingerprints if compromised? Biodata is the least secure because it can't be easily changed and the technology already exists to compromise them.

Compromise isn't even the most common issue, it's your incapacity or death. Your relatives need some way to get into your accounts when you can't.

Re: Passkeys will come at a cost

#165

Post by dcow »

torstenvl wrote: post #161

I'm not a security or crypto guy at all. I found this very difficult to follow, and I suspect others might too. My questions probably seem weird to someone with enough background context to understand the post, but I am getting wrapped around the axle every sentence or two. > It all comes down to one thing - resident keys. How/why? What's the connection to passkeys or HSMs? > we need to understand what a discoverable…

It's a poorly argued point, agree. Essentially the author is arguing that the ability in the WebAuthN protocol for Relying Parties to be able to specify `rk=required` is considered harmful because it excludes tons of TPM hardware from being able to work as a Passkey wallet/db. I think most people in the comments probably agree. That doesn't excuse all the confusion the author creates by essentially bike-shedding the definition of passkey for half the essay.

Re: Passkeys will come at a cost

#166

Post by thaumasiotes »

mrtksn wrote: post #159
thaumasiotes wrote: post #158

Earlier quoted context omitted.

> Instead, you assume that the biological being is capable of keeping track of the authentication device and people are naturally good at it. This is not something that people are good at.

Why do you think that?

I have some experience with people trying to keep track of objects.

Re: Passkeys will come at a cost

#167

Post by matthewaveryusa »

deathanatos wrote: post #144
matthewaveryusa wrote: post #29

Earlier quoted context omitted.

It's less that they are limited in memory, and more so that they are designed to not have memory limits. If you look at TPMs, basically each time you want to sign something, your input is the data you want to sign and a sealed private key. The sealed key is the private key that was generated by the TPM and then symmetrically encrypted with the key embedded in the TPM. You store the sealed key in your mass storage, an…

What you're talking about seems to be what the article would call a "non-resident" key, whereas this commenter is specifically asking about "resident" keys. Or, if you think you are describing resident keys, then you need to reconcile, > This design allows you to have as many keys as your mass storage will allow you to save. with the OP: the article states that to be roughly "20", and people tend to have more than 20…

What I'm saying is if you look at the sequence diagram for the resident key, at step 3 there's no requirement to have the keys stored in the security key: you can save an Rp to token mapping in the client outside and it's still considered a resident key.

I think what I'm saying here is that resident means resident to the client, not necessarily resident to the enclave. I took a peek at the spec and they define resident keys as being part of the "client platform" which they take care to clarify as "A single hardware device MAY be part of multiple distinct client platforms" https://www.w3.org/TR/webauthn-2/#client-platform

Re: Passkeys will come at a cost

#168

Post by Melown »

It's all about the FIDO2 hardware attestation. I'd rather use a FIDO2 authenticator with attestation. Call it a passkey or not, I don't want the to use the syncable passkeys without hardware attestation.

Re: Passkeys will come at a cost

#169

Post by mrtksn »

thaumasiotes wrote: post #166
mrtksn wrote: post #159

Earlier quoted context omitted.

Why do you think that?

I have some experience with people trying to keep track of objects.

Can you describe your experience? I know what you mean but if you describe it, I think we will be able to examine the implications.

Re: Passkeys will come at a cost

#170

Post by NotYourLawyer »

> The problem is that security keys with their finite storage and lack of credential management will fill up rapidly. In my password manager I have more than 150 stored passwords. If all of these were to become resident keys I would need to buy at least 5 yubikeys to store all the accounts

How it is possible that THIS is the problem in 2023? Storage is cheap, tiny, and capacious. I feel like I’m reading an article from 1992.

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