The theory of quadratic residues plays an important role in cryptography.In 2001,Cocks developed an identity-based encryption(IBE)scheme based on quadratic residues,resolving Shamir’s 17-year-old open problem.However...The theory of quadratic residues plays an important role in cryptography.In 2001,Cocks developed an identity-based encryption(IBE)scheme based on quadratic residues,resolving Shamir’s 17-year-old open problem.However,a notable drawback of Cocks’scheme is the significant expansion of the ciphertext,and some of its limitations have been addressed in subsequent research.Recently,Cotan and Teşeleanu highlighted that previous studies on Cocks’scheme relied on a trial-and-error method based on Jacobi symbols to generate the necessary parameters for the encryption process.They enhanced the encryption speed of Cocks’scheme by eliminating this trialand-error method.Based on security analysis,this study concludes that the security of Cotan-Teşeleanu’s proposal cannot be directly derived from the security of the original Cocks’scheme.Furthermore,by adopting the Cotan-Teşeleanu method and introducing an additional variable as a public element,this study develops a similar enhancement scheme that not only accelerates the encryption speed but also provides security equivalent to the original Cocks’scheme.展开更多
为了使列存储OLAP(on-line analytical processing)操作中I/O和CPU开销较大的扫描、连接、聚集操作实现有效的共享和复用,提出了一个多查询优化技术。根据列存储以及OLAP操作的特点,提出了一系列转换规则,为OLAP查询请求产生的一组相关...为了使列存储OLAP(on-line analytical processing)操作中I/O和CPU开销较大的扫描、连接、聚集操作实现有效的共享和复用,提出了一个多查询优化技术。根据列存储以及OLAP操作的特点,提出了一系列转换规则,为OLAP查询请求产生的一组相关查询语句生成一个单一全局查询计划。为了达到共享复用的目的,在全局计划中引入新的过滤结点、分组结点、合并结点和聚集结点。同时,借用MuGA(multiply group by algo-rithm)算法,通过分组结点、合并结点、连接结点实现维表及事实表元组的分组序号标记,从而实现列扫描、列连接的共享。并为聚集结点提出了一个多阶段聚集算法,结合最终生成的事实表复合分组序号,实现聚集操作的复用。在SSB(star schema benchmark)数据集上设计实验,证明了该多查询优化策略的有效性。展开更多
基金Rising-Star Program of Shanghai 2023 Science and Technology Innovation Action Plan(Yangfan Special Project),China(No.23YF1401000)Fundamental Research Funds for the Central Universities,China(No.2232022D-25)。
文摘The theory of quadratic residues plays an important role in cryptography.In 2001,Cocks developed an identity-based encryption(IBE)scheme based on quadratic residues,resolving Shamir’s 17-year-old open problem.However,a notable drawback of Cocks’scheme is the significant expansion of the ciphertext,and some of its limitations have been addressed in subsequent research.Recently,Cotan and Teşeleanu highlighted that previous studies on Cocks’scheme relied on a trial-and-error method based on Jacobi symbols to generate the necessary parameters for the encryption process.They enhanced the encryption speed of Cocks’scheme by eliminating this trialand-error method.Based on security analysis,this study concludes that the security of Cotan-Teşeleanu’s proposal cannot be directly derived from the security of the original Cocks’scheme.Furthermore,by adopting the Cotan-Teşeleanu method and introducing an additional variable as a public element,this study develops a similar enhancement scheme that not only accelerates the encryption speed but also provides security equivalent to the original Cocks’scheme.
文摘为了使列存储OLAP(on-line analytical processing)操作中I/O和CPU开销较大的扫描、连接、聚集操作实现有效的共享和复用,提出了一个多查询优化技术。根据列存储以及OLAP操作的特点,提出了一系列转换规则,为OLAP查询请求产生的一组相关查询语句生成一个单一全局查询计划。为了达到共享复用的目的,在全局计划中引入新的过滤结点、分组结点、合并结点和聚集结点。同时,借用MuGA(multiply group by algo-rithm)算法,通过分组结点、合并结点、连接结点实现维表及事实表元组的分组序号标记,从而实现列扫描、列连接的共享。并为聚集结点提出了一个多阶段聚集算法,结合最终生成的事实表复合分组序号,实现聚集操作的复用。在SSB(star schema benchmark)数据集上设计实验,证明了该多查询优化策略的有效性。
