In order to solve the challenges of user data security in the cloud computing (storage) environment, many encryption solutions with different features have been presented. Among them, proxy reencryption (PRE) based on public-key infrastructure (PKI) is a promising technology for secure cloud sharing. And identity-based proxy reencryption (IBPRE), which uses identity as the public key, eliminates burdensome certificate management and is, therefore, more preferable. However, most of the current IBPRE schemes only focus on the processing of data sharing while overlooking the functions of authorization revocation and ciphertext update, which are more closely related to the security of data itself. Moreover, the few existing schemes that involve ciphertext update turn out to be impractical because the length of ciphertext increases with the reencryption of ciphertext. In this paper, an improved IBPRE scheme, which provides improvements on the inadequacies of the scheme proposed by Ateniese et al. especially in terms of collusion safety and ciphertext evolution, is proposed. To the best of our knowledge, this is a practical IBPRE scheme integrating the functions of access authorization, delegation revocation, ciphertext update, reauthorization, and conditional reservation delegation. The proposed technique has high practicability in the scenario where a large number of ciphertexts need to be updated synchronously. Lastly, the comparative analysis and simulation results show that the two reencryption algorithms in the proposed scheme have the shortest computing time than other schemes.

中文翻译：

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基于密谋的基于密谋的身份验证代理重加密方案，用于安全的云共享

为了解决云计算（存储）环境中用户数据安全的挑战，提出了许多具有不同功能的加密解决方案。其中，基于公钥基础结构（PKI）的代理重新加密（PRE）是用于安全云共享的有前途的技术。使用身份作为公钥的基于身份的代理重新加密（IBPRE）消除了繁琐的证书管理，因此更为可取。但是，当前的大多数IBPRE方案仅专注于数据共享的处理，而忽略了授权吊销和密文更新的功能，而这些功能与数据本身的安全性关系更为密切。此外，很少有涉及密文更新的现有方案是不切实际的，因为密文的长度随着密文的重新加密而增加。本文提出了一种改进的IBPRE方案，该方案改进了Ateniese等人提出的方案的不足之处。特别是在合谋安全性和密文演变方面，提出了建议。据我们所知，这是一个实用的IBPRE方案，集成了访问授权，委托吊销，密文更新，重新授权和条件保留委托的功能。在需要同步更新大量密文的情况下，该技术具有较高的实用性。最后，