Applied Cryptography and Network Security pdf

Applied Cryptography and Network Security Wonderful Digest

1.1 Paper Organization

The remainder of this paper is organized as follows. In Section 2, we discuss our approach to the problem, examine the threat model, and provide a security analysis. In Section 3 we discuss in detail the implementation of CamouflageFS as a variant of the Linux Ext2fs,and Section 4 presents some preliminary performance measurements of the system. We give an overview of the related work on cryptographic and steganographic file systems in Section 5. We discuss our plans for future work in Section 6, and conclude the paper in Section 7.

2 Our Approach

Our primary insight is that a user may decrease the performance penalty they pay for employing a cryptographic file system by using only part of the key for cryptographic operations. The rest of the key may be used to unpredictably spread the data into the file’s address space. Note that we are not necessarily fragmenting the placement of the data on disk, but rather mixing the placement of the data within the file.

2.1 Key Composition: Maintaining Confidentiality

While our goal is to mitigate the performance penalty paid for using a cryptographic file system, it is not advisable to trade confidentiality for performance. Instead, we argue thatkeys can be made effectively longer without incurring the usual performance penalty. One obvious method of reducing the performance penalty for encrypting files is to utilize a cipher with a shorter key length; however, there is a corresponding loss of confidentiality with a shorter key length. We address the tradeoff between key length and performance by extending the key with “spreading bits,” and exploiting the properties of an indexed allocation file system.