It is the most important and challenging problem to share the data safely in cloud computing. Some so-called trusted third parties may also infringe users’ data privacy. It is an urgent problem for data owners to share data safely with the designated users rather than the third party or other users. Traditional encryption schemes utilize different keys to produce multiple encrypted copies of the same data for users. It is no longer applicable for cloud data sharing security. Attribute-based encryption can solve above problems, but it needs to rely on trusted third parties to protect the users’ privacy. In this article, in order to address the above problems, we propose a blockchain-based ciphertext-policy attribute-based encryption scheme for cloud data secure sharing without relying on any trusted third parties. Blockchain-based ciphertext-policy attribute-based encryption scheme can protect the rights and security of data owner. Compared with existing cloud security schemes, the proposed scheme has more advantages in terms of the six aspects: (1) data owners have the authority to decide who can decrypt the data; (2) the operations of users are retained permanently, and all records are tamper-proof; (3) our proposed scheme has the characteristic of “one-to-many” encryption, and data is encrypted only once; (4) our scheme does not rely on any trusted third party; (5) in terms of the discrete logarithm problem and decisional q parallel-bilinear Diffie–Hellman exponent problem, we prove that our proposed scheme is secure; and (6) experiment shows that our proposed scheme is more efficient than the comparative scheme.

在云计算中安全共享数据是最重要和最具挑战性的问题。一些所谓的受信任的第三方也可能侵犯用户的数据隐私。对于数据所有者而言，与指定用户而不是第三方或其他用户安全地共享数据是一个迫在眉睫的问题。传统的加密方案利用不同的密钥为用户生成同一数据的多个加密副本。它不再适用于云数据共享安全性。基于属性的加密可以解决上述问题，但是它需要依赖受信任的第三方来保护用户的隐私。在本文中，为了解决上述问题，我们提出了一种基于区块链的基于密文策略的基于属性的加密方案，用于云数据安全共享，而无需依赖任何受信任的第三方。基于区块链的密文策略基于属性的加密方案可以保护数据拥有者的权利和安全。与现有的云安全方案相比，该方案在六个方面具有更多的优势：（1）数据所有者有权决定谁可以解密数据；（2）永久保留用户的操作，并且所有记录都是防篡改的；（3）我们提出的方案具有“一对多”加密的特点，数据仅加密一次；（4）我们的计划不依赖任何受信任的第三方；（5）从离散对数问题和判定q并行-双线性Diffie-Hellman指数问题，我们证明了所提出的方案是安全的；（6）实验表明，我们提出的方案比比较方案更有效。