The special IMI Colloquium in December was held on December 19, 2019. | The special IMI Colloquium in December | Title : **On the cryptosystem in Quantum Computer era** | Speaker : Dr. Koichiro AKIYAMA (TOSHIBA Corporation R&D Center) | Place : IMI Auditorium (W1-D-413) (4F, West Zone 1, Kyushu University) | | In this lecture, “Post-Quantum Cryptography”, in particular the social needs, its representative systems and issues, were introduced. This cryptography can maintain the safety of networks in the quantum computer era. The speaker also talked about a new cryptography called “indefinite equation cryptography” as a collaborative work. Lattice-based cryptography, which is one of influential post-quantum cryptography, is supposed to be secure due to computational difficulty of closest vector finding problems over vector spaces. But it has “large key-size problem compared with present cryptography” to keep safety, since the underlying problem is linear. The speaker proposes new public key cryptography using “nonlinear” indefinite equations over a certain kind of commutative rings. These concepts are based on the theory of commutative algebra and integer theory, which recognize us the great importance of abstract mathematics based on algebra towards new technology in the next generation. Attendance: Staff 10, Students 24 | | | | The special IMI Colloquium in December Photos. If you click each image, the big image appears． | | | | | | | |