《《sc-iphone-passwords》.pdf

Lost iPhone? Lost Passwords! Practical Consideration of iOS Device Encryption Security Jens Heider, Matthias Boll Fraunhofer Institute for Secure Information Technology (SIT) February 9, 2011 Abstract The paper highlights risks that accompany losing a locked iOS device regarding confidentiality of passwords stored in the keychain. It presents results of hands- on tests that show the possibility for attackers to reveal some of the keychain entries. For the described approach, the knowledge of the user’s secret pass- code is not needed, as the protection provided by the passcode is bypassed. 1 Introduction During many discussions about security of iOS devices (iPhone, iPad) we have recognized that the public perception of protection strength provided by the iOS device encryption does not reflect all aspects of the security for stored passwords, which we consider important. Therefore, this paper is intended to point out related facts, which were elaborated by hands-on tests to clarify the strength of the protection in a lost device scenario. When an iOS device with hardware encryption capabilities is lost or stolen, many users believe that there is no way for a new owner to access the stored data — at least if a strong passcode 1 is in place. This estimation is comprehen- sible, since in theory the cryptographic strength of the AES-256 algorithm used for iOS device encryption should prevent even well equipped attackers. How- ever, it was already shown2 that it is possible to access great portions of the stored data without knowing t