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I'm very skeptical that traditional screen-lock passcodes offer useful protection for the average person. Most people still choose to use 4-digit passcodes for

by ckuehl 12y ago

I'm very skeptical that traditional screen-lock passcodes offer useful protection for the average person. Most people still choose to use 4-digit passcodes for convenience, leaving exhaustive key search [1] well within the reach of even very small attackers. Are these four-digit passcodes being used to derive encryption keys? If so, I'd like to hear where the additional entropy comes from. There's no use encrypting things with a 128-bit key when the effective entropy of the key is really only ~12.3 bits. I'm sure the engineers at Apple would not have overlooked this; it would be great to hear more about the specifics. [1] especially if the attacker can download encrypted data and try an infinite number of times (instead of e.g. typing the passcode on the phone or hitting the iCloud servers)

wyager 12y ago
IIRC, there are three crypto keys involved: 1. PIN 2. Random key in effaceable NAND storage (generated on device reset) 3. Burned in permanent CPU-unique key. I think OP's linked statement from Apple means that Apple is now also encrypting data stored on the iCloud servers. http://www.apple.com/ipad/business/docs/iOS_Security_Feb14.pdf http://www.apple.com/ipad/business/docs/iOS_Security_Feb14.p...
- declan 12y ago
  >I think OP's linked statement from Apple means that Apple is now also encrypting data stored on the iCloud servers. From today's announcement (scroll to "iCloud"): Mail and Notes are not stored in encrypted form on iCloud servers. http://www.apple.com/privacy/privacy-built-in/ http://www.apple.com/privacy/privacy-built-in/ From December 2013: Mail and Notes are not stored in encrypted form on iCloud servers. http://support.apple.com/kb/HT4865 http://support.apple.com/kb/HT4865
  - wyager 12y ago
    Then what has changed?
    - declan 12y ago
      This is a very good question. I'm now no longer sure.
  - robszumski 12y ago
    Just to be clear, we're talking about mail sent with an @icloud.com or @me.com address, right? Surely all IMAP traffic doesn't flow through their servers.
- dunham 12y ago
  And this means the passcode has to be broken on the device. The key is generated from the passcode and the other keys you mention via PBKDF2, which slows down the cracking process. You also have to have a non-destructive jailbreak or Apple's update-signing key to do the cracking. I'd recommend using a longer passcode. If you don't want to use the keyboard, choose a long number for a passcode and you will still get a number-pad when entering it. Another loophole to be aware of is the "escrow keybag". If you're paired with a laptop, there is a file in /var/db/lockdown that can work in place of the PIN (the device can decrypt the escrow keybag with #2 and #3 above and use the keys therein to decrypt the files it needs). Apple did this to allow backups without unlocking the device.

by ckuehl 12y ago

wyager 12y ago

IIRC, there are three crypto keys involved: 1. PIN 2. Random key in effaceable NAND storage (generated on device reset) 3. Burned in permanent CPU-unique key. I think OP's linked statement from Apple means that Apple is now also encrypting data stored on the iCloud servers. http://www.apple.com/ipad/business/docs/iOS_Security_Feb14.pdf http://www.apple.com/ipad/business/docs/iOS_Security_Feb14.p...

declan 12y ago
>I think OP's linked statement from Apple means that Apple is now also encrypting data stored on the iCloud servers. From today's announcement (scroll to "iCloud"): Mail and Notes are not stored in encrypted form on iCloud servers. http://www.apple.com/privacy/privacy-built-in/ http://www.apple.com/privacy/privacy-built-in/ From December 2013: Mail and Notes are not stored in encrypted form on iCloud servers. http://support.apple.com/kb/HT4865 http://support.apple.com/kb/HT4865
- wyager 12y ago
  Then what has changed?
  - declan 12y ago
    This is a very good question. I'm now no longer sure.
- robszumski 12y ago
  Just to be clear, we're talking about mail sent with an @icloud.com or @me.com address, right? Surely all IMAP traffic doesn't flow through their servers.
dunham 12y ago
And this means the passcode has to be broken on the device. The key is generated from the passcode and the other keys you mention via PBKDF2, which slows down the cracking process. You also have to have a non-destructive jailbreak or Apple's update-signing key to do the cracking. I'd recommend using a longer passcode. If you don't want to use the keyboard, choose a long number for a passcode and you will still get a number-pad when entering it. Another loophole to be aware of is the "escrow keybag". If you're paired with a laptop, there is a file in /var/db/lockdown that can work in place of the PIN (the device can decrypt the escrow keybag with #2 and #3 above and use the keys therein to decrypt the files it needs). Apple did this to allow backups without unlocking the device.