TransCrypt: Design of a Secure and Transparent Encrypting File System


Increasing thefts of sensitive data owned by individuals and organizations call for an integrated solution to the problem of storage security. Most existing systemsare designed for personal use and do not address the unique demands of enterprise environments. An enterprise-class encrypting file system must take a cohesive approach towards solving the issues associated with data security in organizations. These include flexibility for multi-user scenarios, transparent remote access of shared file systems and defense against an array of threats including insider attacks while trusting the fewest number of entities.

In this thesis, we formalize a general threat model for storage security and discuss how existing systems that tackle a narrow threat model are thus susceptible to attacks. We present the conceptualization, design and implementation of {\em TransCrypt,} a kernel-space encrypting file system that incorporates an advanced key management scheme to provide a high grade of security while remaining transparent and easily usable. It examines difficult problems not considered by any existing system such as avoiding trusting the superuser account or privileged user-space process and proposes novel solutions for them. These enhancements enable TransCrypt to protect against a wider threat model and address several lacunae in existing systems.

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Introduction
The need for data security emerges from the widespread deployment of shared file
systems, greater mobility of computers and the rapid miniaturization of storage devices.
It is increasingly obvious that the value of data is much more than the value of
the underlying devices. The theft of a personal laptop or a USB thumbdrive leaves
the victim vulnerable to the risk of identify theft in addition to the loss of personal
or financial data and intellectual property. Several recent incidents of data theft emphasize
the need for a cohesive solution to the problem of storage security. Hence,
it is fast becoming necessary to protect stored data from unauthorized access using
strong cryptographic methods.
1.1 Motivation for Data Security
An enterprise-ready data protection system is vital in military organizations where
classified and secret data need to be shared and secured simultaneously. Recent news
reports of security breaches and data thefts from India’s military and intelligence
agencies [2] accentuate the critical need for a cryptographic solution to this problem.
According to reports relating to one case, important information was leaked through
stolen USB thumbdrives. Another case purportedly involved a computer administrator
who was able to pass secret data illegitimately to a foreign country. The fact that
both these cases involved insiders motivates the need for a secure data protection
mechanism that thwarts theft attempts and ensures that undue power is not left in
the hands of individual employees or administrators.
Data protection systems are increasingly playing a crucial role in commercial
environments too. A recent study conducted by Symantec Corporation [18] surveyed
laptop users across Europe, the Middle East and Africa to estimate the value of the
commercially sensitive contents of their laptops. The study estimated the average
worth of a single laptop to be about a million dollars.
Clearly, there is a pressing need to design and develop secure and usable data
protection mechanisms that cater to the above application scenarios. Encrypting file
systems fill this void to enable individuals and organizations to keep their storage
systems highly available and protected from unauthorized access at the same time.