Recently, three scientific research achievements made by the ECNU Software Engineering Institute were presented at EUROCRYPT 2020 and CRYPTO 2020, two top international cryptography conferences organized by the International Association for Cryptologic Research (IACR).

Two of them, “Adaptively Secure ABE for DFA from k-Lin and More” and “Functional Encryption for Attribute-Weighted Sums from k-Lin”, were contributed by Dr. Gong Junqing, a young ECNU teacher, in collaboration with two scholars from the École Normale Supérieure (ENS, Paris).

The works studied two cryptographic primitives, attribute-based encryption (ABE) and functional encryption (FE), which are useful to the fine-grained access control and computation over encrypted data. The main contributions are new techniques to support the policy (for ABE) and functionality (for FE) that can handle unbounded-size inputs, which is a desirable feature for various applications in the new era.

Gong Junqing

After obtaining his PhD from Shanghai Jiaotong University in 2016, Dr. Gong Junqing went to France for postdoctoral studies, and worked at the École Normale Supérieure de Lyon (ENS de Lyon) and École Normale Supérieure (ENS, Paris) in succession. He has long been engaged in the research of attribute-based encryption and functional encryption.

Since Keccak was selected as the SHA-3 standard, more and more permutation-based primitives have been proposed. And there is no round key in the underlying permutation for permutation-based primitives. Therefore, there is a higher risk for a differential characteristic of the underlying permutation to become incompatible if we consider the dependency of difference transitions over different rounds. However, in most of the MILP or SAT based models to search for differential characteristics, only the difference transitions are involved and are treated as independent in different rounds.

To overcome this obstacle, ECNU researchers are motivated to design a model which automatically avoids inconsistency in the search for differential characteristics. Their work "Automatic Verification of Differential Characteristics: Application to Reduced Gimli" was also published at  CRYPTO 2020.  Liu Fukang, a PhD student in Prof. Cao Zhenfu's team from the Software Engineering Institute, is the first-author of this paper.

Liu Fukang

The International Association for Cryptologic Research (IACR) is a non-profit scientific organization whose purpose is to further research in cryptology and related fields.