Dr. Donghoon Chang (NIST & Strativia, USA)

Donghoon Chang received B.S. degree in mathematics from Korea University in 2001, and M.S. and Ph.D. degrees in information security from Korea University in 2003 and 2008, respectively. He was a postdoc researcher in Columbia University, USA, from 2008 to 2009. From 2009 to 2012, he was a guest researcher of NIST, USA. He was an assistant professor (June 2012-2016) and a tenured associate professor (2017- July 2024) of Indraprastha Institute of Information Technology Delhi (IIIT-Delhi), India. From May 2019 to July 2021, he was a guest researcher of NIST, USA. Since August 2021, he has been working as a research scientist (NIST associate) at Strativia, USA. His research interests are cryptanalysis, provable security of cryptographic algorithms, and biometric security.

Title - Accordion Mode Development

Abstract - In 2023 and 2024, NIST held two workshops to discuss the development of an Accordion Mode based on a block cipher. NIST published a discussion draft for a proposal of requirements for an Accordion Mode. In this talk, I will first share the historical background to explain why NIST considers an Accordion mode, then review the previous two workshops, and finally, discuss the next steps moving forward.

     Dr. Yu Sasaki (NTT, Japan)

Yu Sasaki received Bachelor of Engineering and Master of Engineering from The University of Electro-Communications in 2005 and 2007. In 2010, he received Ph.D. degrees from The University of Electro-Communications, focusing on the symmetric-key cryptography Since 2007, he has been a researcher at NTT Secure Platform Laboratories, where the organization renewed to NTT Social Informatics Laboratories from 2020. From 2015 to 2016, he was a senior research fellow at Nanyang Technological University in Singapore. From 2022, he has been a foreign guest researcher at National Institute of Standards and Technology in US. His current research interests are in cryptography, including design and security analysis of symmetric-key cryptographic schemes. He is the co-designer of SKINNY, which is internationally standardized by ISO.

Title - Committing Security of Authenticated Encryption

Abstract - This talk introduces the notion of committing security, mostly known as key-commitment and context-commitment, for authenticated encryption in symmetric-key cryptography, which intuitively means that a ciphertext generated by a key or decryption context should not be able to be generated with another key or another decryption context. Then, the impact of the attacks breaking committing security is briefly introduced, and known issues on committing security on internationally standardized authenticated encryption schemes are explained. The recent standardization project on block-cipher based wide-block encryption mode, called accordion mode, initiated by NIST showed an interest to provide committing security. The talk explains the recent work about committing security of wide-block encryption mode.