Apple iWork, an inexpensive office productivity suite for the Mac and iOS platforms, has been around since 2005 and 2011 respectively. The iWork suite consists of three apps: Numbers, Pages, and Keynotes, and gained quite some popularity among Apple followers. Yet, for all this time, no one came out with a feasible password recovery solution for the iWork document format.
The reason for the lack of a password recovery solution for the iWork format is extremely slow recovery speed. This owes to Apple’s implementation of encryption: the company used an industry-standard AES algorithm with strong, 128-bit keys. Brute-forcing a 128-bit number on today’s hardware remains impossible. The original, plain-text password has to be recovered in order to decrypt protected iWork documents.
However, recovering that plain-text password is also very slow. Apple used the PBKDF2 algorithm to derive an encryption key from plain-text passwords, with some 4000 iterations of a hash function (SHA1). While it takes only a hundredth of a second to verify a single password, an attack would be speed-limited to about 500 passwords per second on today’s top hardware. This is extremely slow considering the number of possible password combinations.
When starting considering the addition of Apple iWork to the list of supported products, we quickly recognized the speed bottleneck. With as slow a recovery, a distributed attack on the password would be the only feasible one. Indeed, using multiple computers connected to a large cluster gives us more speed, breaking the barrier of unreasonable and promising realistic recovery timeframe. Brute-forcing is still not a good option, but ElcomSoft’s advanced dictionary attack with customizable masks and configurable permutations is very feasible if we consider one thing: the human factor.
The Human Factor
Let’s look at the product one more time. Apple iWork is sold to mobile users for $9.99. Mac customers can purchase the suite for $79. These price points clearly suggest that Apple is targeting the consumer market, not government agencies and not corporations with established security policies enforcing the use of long, complex, strong passwords.
Multiple researches confirm it’s a given fact that most people, if not enforced by a security policy, will choose simple, easy to remember passwords such as ‘abc’, ‘password1’ or their dog’s name. In addition, it’s in the human nature to reduce the number of things to remember. Humans are likely to re-use their passwords, with little or no variation, in various places: their instant messenger accounts, Web and email accounts, social networks and other places from which a password can be easily retrieved.
Considering all this, 500 passwords per second doesn’t sound that bad anymore. Which brings us to the announcement: Elcomsoft Distributed Password Recovery now supports Apple iWork, becoming an industry-first tool and the only product so far to recover passwords for Numbers, Pages and Keynotes apps. It’s the human factor and advanced dictionary attacks that help it recover a significant share of iWork passwords in reasonable time.