Salam,
--
Farshid Farhat
http://ee.sharif.edu/~farhat/
The 30th c-r-y-p-t-o-g-r-a-p-h-y seminar will be held on next Monday (The 11th July, 21 Mordad) at 11am.
Speaker : Hadi Ahmadi
Title: Systematic Guess-and-Determine Attack on Stream Ciphers
Abstarct: Guess-and-Determine (GD) attacks are general attacks on stream
ciphers which have often been implemented heuristically. In this paper we
introduce a systematic approach to design of GD attacks, using a
well-known decoding algorithm for convolutional codes, namely the Viterbi
algorithm. We have shown that with this method, the resulting GD attacks,
named Systematic GD (SGD) attacks, on TIPSY, SNOW1, and SNOW2 need less
number of guess elements in comparison with the previous known GD attacks.
The main advantage of SGD attacks is that while being powerful, they can
be designed systematically for any given LFSR-based stream cipher. Using
this method, we examine the resistance of SOSEMANUK, a word-oriented
stream cipher proposed for the Ecrypt stream cipher project. The
complexity of the designed GD attack indicates SOSEMANUK is still alive,
having the 128-bit security as the authors claimed.
Bio.:
Ph.D. Candidate in Dept. of Computer Science, at University of Calgary
M.Sc. School of Electrical Engineering, Sharif University of Technology
B.Sc. Faculty of Engineering, University of Tehran
Speaker : Hadi Ahmadi
Title: Systematic Guess-and-Determine Attack on Stream Ciphers
Abstarct: Guess-and-Determine (GD) attacks are general attacks on stream
ciphers which have often been implemented heuristically. In this paper we
introduce a systematic approach to design of GD attacks, using a
well-known decoding algorithm for convolutional codes, namely the Viterbi
algorithm. We have shown that with this method, the resulting GD attacks,
named Systematic GD (SGD) attacks, on TIPSY, SNOW1, and SNOW2 need less
number of guess elements in comparison with the previous known GD attacks.
The main advantage of SGD attacks is that while being powerful, they can
be designed systematically for any given LFSR-based stream cipher. Using
this method, we examine the resistance of SOSEMANUK, a word-oriented
stream cipher proposed for the Ecrypt stream cipher project. The
complexity of the designed GD attack indicates SOSEMANUK is still alive,
having the 128-bit security as the authors claimed.
Bio.:
Ph.D. Candidate in Dept. of Computer Science, at University of Calgary
M.Sc. School of Electrical Engineering, Sharif University of Technology
B.Sc. Faculty of Engineering, University of Tehran
--
Farshid Farhat
http://ee.sharif.edu/~farhat/
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