KOYAMA Research Laboratory

[Japanese version]

Dr. Kenji Koyama passed away on March 27, 2000.


We conduct research on theoretical communication science in order to clarify the mechanism of communication. The concrete research themes include Information Security for constructing secure computer network, Emotion Transmission Theory for elucidating mechanism of emotion and impressions in interpersonal communication, Data Compression Theory for clarifying expressing information from the mathematical viewpoint.

Information Security Theory

Use of the public-key cryptosystems is effective to keep privacy and authentication in computer communications. We have invented a public-key cryptosystem based on cubic curves (including elliptic curves). The security of the new scheme is based on the difficulty of integer factorization. We proved that the security of the new scheme is equivalent to that of the RSA scheme. The new scheme is twice as fast as RSA scheme.

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Figure 1: Elliptic curve cryptosystem

(Contact: Yukio Tsuruoka; Email: tsuru@cslab.kecl.ntt.co.jp)

Emotion Transmission Theory

Laughter is one of the most frequent and the most complex emotional expressions of man in everyday life. It is indispensable for smooth human communications. We examined the effect of temporal differences in eye and mouth movements on classifying facial expressions of smiles. We developed the 3-dimensional model using computer graphics. We could verify that these differences significantly influence the classification.
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Figure 2: Movements and classification of smiles

In addition, we confirmed that:

  1. when the mouth begins moving prior to the eyes, the expressions are taken as a smile of pleasantness (positive),
  2. when the eyes move prior to the mouth, the expressions are taken as a smile of unpleasantness (negative),
  3. when both movements begin simultaneously, the expressions are taken as social smiles.

(Contact: Shuichi Nishio; Email: nishio@cslab.kecl.ntt.co.jp)

Recent Topics

Publication List

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Last modified on 31/Mar/2000