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Spatial amplification of information secrecy

IP.com Disclosure Number: IPCOM000189110D
Publication Date: 2009-Oct-28
Document File: 4 page(s) / 33K

Publishing Venue

The IP.com Prior Art Database

Abstract

A scheme is proposed to use Wire-Tap channel II codes in order to improve the security of storing and erasing sensitive data in storage devices. Since sensitive bits are prone to imperfect physical erasure, these codes are used to amplify the security such that no information is leaked even when the erasure is far from perfect. The scheme may be applied to hard-disk drives, solid-state drives, or any other storage medium with imperfect erasure.

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Spatial amplification of information secrecy

Security Amplification of Sensitive-data Storage in
the Presence of Imperfect Physical Erasures
Yuval Cassuto, Zvonimir Bandic, Cyril Guyot and BruceWilson
Hitachi Global Storage Technologies {yuval.cassuto,zvonimir.bandic,cyril.guyot,bruce.wilson}@hitachigst.com
Abstract
A scheme is proposed to use Wire-Tap channel II codes in order to improve the security of storing and erasing sensitive data
in storage devices. Since sensitive bits are prone to imperfect physical erasure, these codes are used to amplify the security such
that no information is leaked even when the erasure is far from perfect. The scheme may be applied to hard-disk drives, solid-state
drives, or any other storage medium with imperfect erasure.

Index Terms
Secure erase, key storage, error-correcting codes, wire-tap channel, hard-disk drive, solid-state drive
I. INTRODUCTION


Imperfect physical erasure is a fundamental problem for security storage devices. In such devices, a secure erasure of the
user data is achieved by erasing the cryptographic keys that were used to encrypt the data, but otherwise leave the actual
encrypted data unerased. As a result, the security of the whole storage device is condensed to the encryption key, making its
complete erasure a crucial design constraint. Unfortunately, the physical-erasure mechanisms are far from perfect, allowing the

possibility of having pieces of the key accessible to a potential adversary after erasure

Consequently, a method is needed to
encode and store the key such that absolutely none of it would leak, even if many of the physical bits are not properly erased.

It turns out that this problem can be solved using a previously known construct in information theory, called codes for the
wire-tap channel II. In the following section, we describe the wire-tap channel II and detail the

process of constructing codes

for that channel. In section III, we show how such codes can be applied to storage devices.
II. THE WIRE-TAP CHANNEL II

The Wire-Tap channel II,

proposed by Ozarow and Wyner in 1984 [3],

framework for the problem
of storing keys that are resilient to partial erasure. Wire-Tap channel II builds upon ideas from

~

Wyner fs original Wire-Tap
channel [5], focusing on security performance from a worst-case perspective. A worst-case analysis means that coding schemes
are secure for any bounded-size subset of the codeword locations that is accessible by the adversary. In this section we briefly

.

provides the suitable

1

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review the definitions and construction methods from [3]. The notation used here is an adaptation of the original one to fit the
current application and constructions. This section requires some elementary facts from the theory of linear error-correcting
codes, thus the reader may feel free to consult any textbook on this topic such as [4],[2],[1] or others.
A. Problem statement and model definition


Let k be the number of bi...