[liberationtech] Infiltrate the Vault: Security Analysis and Decryption of Lion Full Disk Encryption

[Robert Guerra]

Just came across the following research paper that no doubt will be of interest to folks on this list.

Kudos to the team at the University of Cambridge and others who have long been working on taking apart Apple File Vault's volume encryption mechanism.


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Infiltrate the Vault: Security Analysis and Decryption of Lion Full Disk Encryption
http://eprint.iacr.org/2012/374.pdf

Omar Choudary
University of Cambridge

Felix Grobert ¨

Joachim Metz


Abstract 

With the launch of Mac OS X 10.7 (Lion), Apple has introduced a volume encryption mechanism known as FileVault 2. Apple only disclosed marketing aspects of the closed-source software, e.g. its use of the AES-XTS tweakable encryption, but a publicly available security evaluation and detailed description was unavailable until now.

We have performed an extensive analysis of FileVault 2 and we have been able to find all the algorithms and parameters needed to successfully read an encrypted volume. This allows us to perform forensic investigations on encrypted volumes using our own tools.

In this paper we present the architecture of FileVault 2, giving details of the key derivation, encryption process and metadata structures needed to perform the volume decryption. Besides the analysis of the system, we have also built a library that can mount a volume encrypted with FileVault 2. As a contribution to the research and forensic communities we have made this library open source.

Additionally, we present an informal security evaluation of the system and comment on some of the design and implementation features. Among others we analyze the random number generator used to create the recovery password. We have also analyzed the entropy of each 512-byte block in the encrypted volume and discovered that part of the user data was left unencrypted.