Securing Data in iOS(blog.chariotsolutions.com)
blog.chariotsolutions.com
Securing Data in iOS
http://blog.chariotsolutions.com/2012/04/securing-data-in-ios.html
6 comments
The keychain is really great for convenience, though it is dependent on the iOS passcode. Users are free to setup their phones without one, use a weak pin, etc. It's exceedingly rare to see an iOS user with a strong multi-character passphrase. For enhanced security there is really no substitue for a suitably long/strong passphrase.
With regard to the second point, one added benefit of SQLCipher over a roll-your-own solution is that SQLCipher automatically applies PBKDF2 derivation. It handles most of the security under the hood so that the application doesn't need to worry about it.
With regard to the second point, one added benefit of SQLCipher over a roll-your-own solution is that SQLCipher automatically applies PBKDF2 derivation. It handles most of the security under the hood so that the application doesn't need to worry about it.
On iOS keychain access is not dependent on the passcode. Each application has access to its own keychain and cannot access the keychain for other applications. The keychain will still be encrypted even if there is no passcode set.
Perhaps my comment wasn't clear. I agree that its not possible for one application to access another's keychain items. However, this isn't the only attack risk, and access to keychain items in general is based on the passcode. This can be a problem if weak passcodes are used and an attacker can get access to the device. There are some relevant comments in this paper:
http://sit.sit.fraunhofer.de/studies/en/sc-iphone-passwords-...
I agree that this could be a problem but in this paper in order for the attack method to work the developer of the App would need to explicitly set the keychain attribute with the flag "kSecAttrAccessibleAlways", making the keychain data available even when the device is locked, "Otherwise the credentials of the app are not affected by the attack method."
Section 2.15 deals with the conditions under which the Keychain should be considered secure:
- Items are stored with a protection class that makes them only available when the device is unlocked. (see Section 2.14) - A strong passcode of 6 alphanumeric digits is enforced (reduces the risk of brute-force attacks)
The second point is as relevant as the first. The paper goes on to say:
according to [App10b]: ... The standard simple code of 4 numeric digits would be brute-forced in less than 9 minutes. Based on the assumption that the counter for wrong tries in the iOS can be bypassed, as it is not hardware-based. [BS11b] provides a tool for passcode bruteforce attacks.
Forensic toolkits, like the one from Elcomsoft (http://www.elcomsoft.com/eift.html), are able to recover numeric pass codes and extract data in less than an hour, even on newer devices.
With a weak passcode, which most people use, the keychain does not offer much protection against dedicated attackers with device access.
- Items are stored with a protection class that makes them only available when the device is unlocked. (see Section 2.14) - A strong passcode of 6 alphanumeric digits is enforced (reduces the risk of brute-force attacks)
The second point is as relevant as the first. The paper goes on to say:
according to [App10b]: ... The standard simple code of 4 numeric digits would be brute-forced in less than 9 minutes. Based on the assumption that the counter for wrong tries in the iOS can be bypassed, as it is not hardware-based. [BS11b] provides a tool for passcode bruteforce attacks.
Forensic toolkits, like the one from Elcomsoft (http://www.elcomsoft.com/eift.html), are able to recover numeric pass codes and extract data in less than an hour, even on newer devices.
With a weak passcode, which most people use, the keychain does not offer much protection against dedicated attackers with device access.
1. Using iOS keychain. The nice thing about it is that it's transparent to the user and easy to explain - "we store it he same way Mail app stores your email password".
2. Asking the user to enter a pass phrase and use it as an encryption key. The key here is to resist the urge to hash the phrase to turn it into a key, and instead use a well known key derivation function for the same purpose.