[Cryptography] Security weakness in iCloud keychain

[Kent Borg]

At the end you answer a key question: You would still have me entering 
passwords, but where my example had me entering a half dozen different 
passwords, you say I would enter just one.

You aren't getting rid of passwords, you are just coming up with a way 
to make recycling a single grand master password safe.

Or, safer. It seems you are only aiming to solve the problem of some 
website leaking plaintext of a recycled password.

But back to One Master Password: I don't want that.

Two immediate reasons:

  - I don't trust all the devices and keyboards in my life with such a 
powerful password. I don't trust that they are honest, I don't trust 
they are competent.

  - I currently don't much worry about shoulder-surfing, most passwords 
I enter aren't that important, but there are a few which are, and then I 
do worry who is behind me and whether there could be a camera above me.

Granted, the immediate utility of a Russian mobster learning this 
password is limited, but still a not something I welcome.

A related question: Would there ever be a case where this master 
password you imagine would actually be an encryption key? That is, would 
I have to worry about encrypted copy of any data leaking into a parallel 
key attack? If so, the master password would have to be a nasty one with 
lots of entropy in it.

I see other problems, but this seems a good start.

-kb