 Hi everyone, this is Julie Zhou, a Ph.D. student at Fang Zhijian University. The topic I want to share today is GUC Secure Commitments via Renault Oracles, New Impossibility and Feasibility. It is a joint work with Bing Shengzhang and Quirin Fang Zhijian University and Hongsheng Zhou from Virginia Commonwealth University. Renault Oracles are important in cryptography. Renault Oracles enable highly efficient particles. For example, there are some fashion male heuristic-based zero-knowledge proofs and there are some RO-based OT particles. Renault Oracles is an idealized setup. In real life, people always use hash functions to instantiate the Renault Oracles. The hash functions such as SHAR256 are predefined and can be obtained by people all over the world. That means there might be a group of people using the SHAR256 to execute a zero-knowledge proof. At the same time, there might be another group of people using the same hash function to execute an OT particle. That means in real life applications, Renault Oracles can be seen as a global setup which is available for different particle instances. However, the famous UC framework chase Renault Oracles as a local setup. UC framework is very important in the area of cryptographic particles. However, in the UC framework, the environment cannot have the direct access to the Renault Oracle in the ideal world execution. That means the simulator can simulate the Renault Oracle in the ideal world execution, so the Renault Oracle is only local to the protocol instance. To the justice issue, Kennedy, Doddys, Puss and Wolfish propose the generalized UC short for GUC. In the GUC framework, the environment can have direct access to the Renault Oracle, so the simulator can no longer simulate the Renault Oracle anymore. The Renault Oracle becomes global and is available for the parties from other protocol instances. We study in the GUC framework. More precisely, we study the GUC secure commitment in the global restricted observable RO short for GRRO which is proposed in CGS 14. We study commitment because it is a fundamental crypto primitive and we study the GRRO model because compared to other global Renault Oracles, it provides the reasonable advantage for the simulator. That is, the simulator can see the adversary's queries to the Renault Oracle. And there are many follow-ups since the original work of the GUC secure commitment in the GRRO model. Among them, ORS achieves the minimum round complexity and requires the weakest computational assumptions. It is well known that in the local RO model, the UC secure commitment can be constructed in only two rounds. However, as you can see in this slide, the minimum round of the previous work in the GRRO model is three. Therefore, it is natural for us to ask what is the lower bound on the round complexity of the GUC secure commitment in the GRRO model. Furthermore, if there exists such a lower bound, we are also wondering if we can give round optimal construction on the minimal assumption. To answer the first question, we prove that the lower bound on round complexity for the UC secure commitment in the GRRO model is two. To answer the second question, we give a three round construction on the minimal assumptions in the GRRO model, and we stress that this construction is round optimal. That is the top abstract, and more details will be given in the follow talk, and more details can be found in the e-print version of our paper. That's all. Thanks for your listening.