2:30-3:30 pm

Room 8405, CUNY Graduate Center

365 Fifth Avenue at 34th Street

Room Peirce 220, Stevens Institute of Technology

Hoboken, NJ

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Security seminars at Stevens

**January 29 (Tuesday!), 4:00, Room Peirce 116, Stevens
Institute**: Alexander V. Mikhalev (Moscow University),
*Codes and recurrent sequences over rings and modules*

**Abstract: **

**February 29, Graduate Center**: Ionut Florescu (Stevens
Institute), *Looking at the Diffie-Hellman key exchange protocol from a
statistical perspective*

**Abstract: **In this talk we will analyze the statistics of the Diffie-Hellman
key exchange.
More precisely, we will try to answer the question: is the conditional
distribution of the key given the information observed uniform on
elements of the underlying groups? The study considers small sized
groups
included in the multiplicative group Z_p. When looked at the
ensemble a picture seems to form that relates the security of the
exchange
with the structure of the underlying group. More empirics are relating
some
of the ideas here with the Discrete Logarithm problem in the same
groups. A
drawback of the study is the absence of the analysis using large order
groups. This may be subject of a future work.
This is joint work with Alex Miasnikov and Ayan Mahalanobis.

**March 14, Graduate Center**: Ayan Mahalanobis (Stevens Institute),
*The MOR cryptoystem and special linear groups over finite fields*

**Abstract: ** The ElGamal cryptosystem is in the heart of public key cryptography. It
is known that the MOR cryptosysetm generalizes it from the cyclic group
to the automorphism group of a (non-abelian) group. I will start by
describing the MOR cryptosystem and then we will use the special linear
group over a finite field as the platform group.
It seems likely that this project is competitive with the elliptic
curves over finite fields in terms of security. I'll explain why I
think so. Then we can talk about challenges in implementation of this
cryptosystem.

**April 4, Stevens Institute, Room Babbio 219**: Ki Hyoung Ko (KAIST,
Korea), *
A polynomial-time solution to the reducibility problem*

**Abstract: ** We present an algorithm for deciding whether a given braid is pseudo-Anosov, reducible,
or periodic. The algorithm is based on Garside's weighted decomposition and is polynomial-time in both the
word-length and the braid index of an input braid. We believe that this algorithm is one of essential steps
toward a polynomial solution to the conjugacy problem in the braid groups.

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