报告人：凌云浩、张益坚、闫佳运

报告地点：淦昌苑D座320，腾讯会议号：102-318-805

报告时间：2024-06-08 9:00-12:00

报告一：Public-key Encryption with Keyword Search in Multi-User, Multi-Challenge Setting under Adaptive Corruptions

报告人：凌云浩

报告摘要：

In the past decade, much progress has been made on proposing encryption schemes with multi-user security. However, no known work aims at constructing a Public-key Encryption with Keyword Search (PEKS) scheme that is secure in multi-user setting. PEKS is a well-known primitive to solve the problem of searching over encrypted data. In this paper, we fill the gap. For more realistic multi-user scenario, we consider a strong security notion. Specifically, the adversary can adaptively corrupt some users' secret keys, and can adaptively request searchable ciphertexts of related keywords under different public keys as well as trapdoors of related keywords under different secret keys. We present two multi-user PEKS schemes both under simple assumptions in the standard model to achieve this strong security notion.

Technically, our first scheme is a variation of the Lewko-Waters identity-based encryption scheme, and our second scheme is a variation of the Wee identity-based encryption scheme. However, we need to prove that the presented public key encryption schemes are secure in the multi-user, multi-challenge setting under adaptive corruptions. We modify the dual system encryption methodology to meet the goal. In particular, the security loss is constant.

报告人简介：

凌云浩，华东师范大学在读博士。研究兴趣为公钥密码理论与应用，特别是可证明安全，紧规约，函数加密（IBE、ABE），可搜索加密，代理重加密。多篇论文发表在PKC，ACISP，Information Sciences，The Computer Journal，Computer Networks等国际会议和期刊。

报告二：Registered Attribute-Based Signature

报告人：张益坚、闫佳运

报告摘要：

This paper introduces the notion of registered attribute-based signature (registered ABS). Distinctly different from classical attribute-based signature (ABS), registered ABS allows any user to generate their own public/secret key pair and register it with the system. The key curator is critical to keep the system flowing, which is a fully transparent entity that does not retain secrets. Our results can be summarized as follows.

This paper provides the first definition of registered ABS, which has never been defined.

This paper presents the first generic fully secure registered ABS over the prime-order group from 𝑘-Lin assumption under the standard model, which supports various classes of predicate.

This paper gives the first concrete registered ABS scheme for arithmetic branching program (ABP), which achieves full security in the standard model.

Technically, our registered ABS is inspired by the blueprint of Okamoto and Takashima[PKC'11]. We convert the prime-order registered attribute-based encryption (registered ABE) scheme of Zhu et al.[ASIACRYPT'23] via predicate encoding to registered ABS by employing the technique of re-randomization with specialized delegation, while we employ the different dual-system method considering the property of registration. Prior to our work, the work of solving the key-escrow issue was presented by Okamoto and Takashima[PKC'13] while their work considered the weak adversary in the random oracle model.

报告人简介：

张益坚，本科毕业于苏州大学数学科学学院，现为华东师范大学软件工程学院硕士研究生，未来将前往澳大利亚伍伦贡大学继续深造。研究兴趣主要包括属性基加密、函数加密和属性基签名。已在PKC 2024发表论文一篇。

闫佳运，2022年于合肥工业大学数学学院获得数学硕士学位，现于华东师范大学软件工程学院密码与网络安全系攻读网络安全博士学位。研究兴趣为公钥密码，具体包括属性基加密、函数加密等。

邀请人：钱宸

审核人：魏普文