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<h3><img src="cid:part1.06020009.01070303@ruhr-uni-bochum.de"
alt="HGI" height="106" align="right" width="116"><br>
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<big><big><big><small>Sehr geehrte Damen und Herren, <br>
<br>
<br>
im Rahmen des HGI-Kolloquiums, organisiert vom
Lehrstuhl Kryptologie und IT-Sicherheit (CITS), wird<br>
<br>
<big><u>Benedikt Driessen und Ralf Hund</u></big></small><u><br>
<br>
</u><small>von der <br>
<br>
Ruhr </small></big></big></big><big><big><big><small>Universität</small></big></big></big><big><big><big><small>
Bochum<br>
<br>
am <br>
<br>
nächsten <u>Donnerstag, den 02. Februar 2012
um 11.00 Uhr s.t. in Raum ID 04/653<br>
<br>
</u>über folgendes Thema referieren:</small><br>
</big></big></big> <br>
<br>
<hr size="2" width="100%">
<h1><small>Don't Trust Satellite Phones<br>
</small></h1>
<big>There is a rich body of work related to the security
aspects of cellular mobile phones, in particular with
respect to the GSM and UMTS systems. To the best of our
knowledge, however, there has been no investigation of the
security of satellite phones (abbr. satphones). Even though
a niche market compared to the G2 and G3 mobile systems,
there are several 100,000 satphone subscribers worldwide.
Given the sensitive nature of some of their application
domains (e.g., natural disaster areas or military
campaigns), security plays a particularly important role for
satphones. In this paper, we analyze the encryption systems
used in the two existing (and competing) satphone standards,
GMR-1 and GMR-2. The first main contribution is that we were
able to completely reverse engineer the encryption
algorithms employed. Both ciphers had not been publicly
known previously. We describe the details of the recovery of
the two algorithms from freely available DSP-firmware
updates for satphones, which included the development of a
custom disassembler and tools to analyze the code, and
extending prior work on binary analysis to efficiently
identify cryptographic code. We note that these steps had to
be repeated for both systems, because the available binaries
were from two entirely different DSP processors. Perhaps
somewhat surprisingly, we found that the GMR-1 cipher can be
considered a proprietary variant of the GSM A5/2 algorithm,
whereas the GMR-2 cipher is an entirely new design. The
second main contribution lies in the cryptanalysis of the
two proprietary stream ciphers. We were able to adopt known
A5/2 ciphertext-only attacks to the GMR-<br>
1 algorithm with an average case complexity of 232 steps.
With respect to the GMR-2 cipher, we developed a new attack
which is powerful in a known-plaintext setting. In this
situation, the encryption key for one session, i.e., one
phone call, can be recovered with approximately 50?65 bytes
of key stream and a moderate computational complexity. A
major finding of our work is that the stream ciphers of the
two existing satellite phone systems are considerably weaker
than what is state-of-the-art in symmetric cryptography.</big><br>
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class="Apple-style-span" style="color: rgb(0, 53, 96);"> </span></span><span
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word-spacing: 0px;"><span class="Apple-style-span"
style="color: rgb(0, 53, 96);"><big>Der Vortrag beginnt am
Donnerstag um 11.00 Uhr s.t. im ID 04/653.<br>
</big></span></span><br>
<span class="Apple-style-span" style="border-collapse:
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class="Apple-style-span" style="color: rgb(0, 53, 96);"><big>Zu
diesem und sämtlichen weiteren Vorträgen im Rahmen des
HGI-Kolloquiums sind alle Studierenden und
Interessierten herzlich eingeladen! Eine Voranmeldung
ist nicht erforderlich!</big></span></span>
<p><span class="Apple-style-span" style="border-collapse:
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class="Apple-style-span" style="color: rgb(0, 53, 96);"><big>Weitere
Informationen gibt es auf folgender Webseite:<br>
<br>
<a
href="http://hgi.rub.de/hgi/hgi-seminar/aktuelles/">http://hgi.rub.de/hgi/hgi-seminar/aktuelles/</a></big><br>
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<big><big>Beste Grüße, <br>
Saqib A. Kakvi</big></big><br>
<br>
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