Attribute based encryption (ABE) is a popular cryptographic technology to protect the security of users’ data. However, the decryption cost and ciphertext size restrict the application of ABE in practice. For most existing ABE schemes, the decryption cost and ciphertext size grow linearly with the complexity of access structure. This is undesirable to the devices with limited computing capability and storage space. Outsourced decryption is considered as a feasible method to reduce the user's decryption overhead, which enables a user to outsource a large number of decryption operations to the cloud service provider (CSP). However, outsourced decryption cannot guarantee the correctness of transformation done by the cloud, so it is necessary to check the correctness of outsourced decryption to ensure security for users’ data. Current research mainly focuses on verifiability of outsourced decryption for the authorized users. It still remains a challenging issue that how to guarantee the correctness of outsourced decryption for unauthorized users. In this paper, we propose an ABE scheme with verifiable outsourced decryption (called full verifiability for outsourced decryption), which can simultaneously check the correctness for transformed ciphertext for the authorized users and unauthorized users. The proposed ABE scheme with verifiable outsourced decryption is proved to be selective CPA-secure in the standard model.

中文翻译：

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基于属性的加密外包解密的完全可验证性

基于属性的加密（ABE）是一种流行的加密技术，用于保护用户数据的安全。然而，解密成本和密文大小限制了 ABE 在实践中的应用。对于大多数现有的 ABE 方案，解密成本和密文大小随着访问结构的复杂性线性增长。这对于计算能力和存储空间有限的设备来说是不可取的。外包解密被认为是一种降低用户解密开销的可行方法，它使用户可以将大量解密操作外包给云服务提供商（CSP）。但是，外包解密并不能保证云端进行转换的正确性，因此需要对外包解密的正确性进行检查，以确保用户数据的安全。目前的研究主要集中在授权用户外包解密的可验证性。如何保证非授权用户外包解密的正确性仍然是一个具有挑战性的问题。在本文中，我们提出了一种具有可验证外包解密（称为外包解密完全可验证性）的ABE方案，该方案可以同时检查授权用户和未授权用户的转换密文的正确性。所提出的具有可验证外包解密的 ABE 方案在标准模型中被证明是选择性 CPA 安全的。我们提出了一种具有可验证外包解密（称为外包解密完全可验证性）的ABE方案，该方案可以同时检查授权用户和未授权用户的转换密文的正确性。所提出的具有可验证外包解密的 ABE 方案在标准模型中被证明是选择性 CPA 安全的。我们提出了一种具有可验证外包解密（称为外包解密完全可验证性）的ABE方案，该方案可以同时检查授权用户和未授权用户的转换密文的正确性。所提出的具有可验证外包解密的 ABE 方案在标准模型中被证明是选择性 CPA 安全的。