[Cryptography] Security weakness in iCloud keychain

[Bill Frantz]

I'm reading the comments about the evils of storing passwords 
with somewhat rye amusement. Here we have what is generally 
considered a really bad authentication mechanism where you don't 
need to have the computer store the secret. When we go to 
stronger authentication, it is much more likely that we will 
need to have the computer store the secret. Consider:

(1) Signed challange with public key crypto, user certs, or 
other similar trickery. The secret key probably needs to be 
stored in the computer because very very few people could 
remember it, or even copy it correctly from a piece of paper 
into the computer. If the secret is in an enclave/TCM, you have 
authenticated the computer and not the user -- which may be the 
correct behavior for some applications.

(2) Two factor authentication using a cell phone: These schemes 
usually use a password + a nonce sent to the cell phone. Good 
for low and medium security applications, but a nation state 
attacker could intercept the call.

Are there any schemes that we should consider?

Cheers - Bill

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Bill Frantz        |"Web security is like medicine - trying to 
do good for
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