4 research outputs found
New Weaknesses in the Keystream Generation Algorithms of the Stream Ciphers TPy and Py
The stream ciphers Py, Py6 designed by Biham and Seberry were promising candidates in the
ECRYPT-eSTREAM project because of their impressive speed. Since their publication in April
2005, a number of cryptanalytic weaknesses of the ciphers have been discovered. As a
result, a strengthened version Pypy was developed to repair these weaknesses; it was
included in the category of `Focus ciphers\u27 of the Phase II of the eSTREAM competition.
However, even the new cipher Pypy was not free from flaws, resulting in a second redesign.
This led to the generation of three new ciphers TPypy, TPy and TPy6. The designers claimed
that TPy would be secure with a key size up to 256 bytes, i.e., 2048 bits. In February
2007, Sekar \emph{et al.\ }published an attack on TPy with data and comparable
time. This paper shows how to build a distinguisher with key/IVs and one
outputword for each key (i.e., the distinguisher can be constructed within the design
specifications); it uses a different set of weak states of the TPy. Our results show that distinguishing attacks with complexity lower than the brute force
exist if the key size of TPy is longer than 268 bits. Therefore, for
longer keys, our attack constitutes an academic break of the cipher.
Furthermore, we discover a large number of similar bias-producing
states of TPy and provide a general framework to compute them. The
attacks on TPy are also shown to be effective on Py
Security of Electrical, Optical and Wireless On-Chip Interconnects: A Survey
The advancement of manufacturing technologies has enabled the integration of
more intellectual property (IP) cores on the same system-on-chip (SoC).
Scalable and high throughput on-chip communication architecture has become a
vital component in today's SoCs. Diverse technologies such as electrical,
wireless, optical, and hybrid are available for on-chip communication with
different architectures supporting them. Security of the on-chip communication
is crucial because exploiting any vulnerability would be a goldmine for an
attacker. In this survey, we provide a comprehensive review of threat models,
attacks, and countermeasures over diverse on-chip communication technologies as
well as sophisticated architectures.Comment: 41 pages, 24 figures, 4 table
Improved cryptanalysis of Py
We improve on the best known cryptanalysis of the stream cipher Py by using a hidden Markov model for the carry bits in addition operations where a certain distinguishing event takes place, and constructing from it an "optimal distinguisher" for the bias in the output bits which makes more use of the information available. We provide a general means to e#ciently measure the e#cacy of such a hidden Markov model based distinguisher, and show that our attack improves on the previous distinguisher by a factor of 2 in the number of samples needed. Given 2 bytes of output we can distinguish Py from random with advantage greater than 2 , or given only a single stream of 2 bytes we have advantage 0.03