JISE

Outsource computing might reveal some private information in open cloud systems and the concern of users' privacy will be a crucial issue. Program obfuscation is an important cryptographic primitive that perfectly hides the secrets inside a program while preserving its functionality. In this paper, we give a two-form re-encryption scheme that achieves the security against adaptively chosen-ciphertext attacks, which allows any third party (e.g., cloud server) to re-encrypt the ciphertext that delegates the decryption right from one to another. However, as the third party knows the sensitive secret (i.e., re-key), and thus we should guarantee the trustworthy of this cloud server. Based the re-encryption algorithm, we propose an efficient obfuscator that implements the re-encryption functionality in such a way that not only the private information is protected but also cloud users’ privacy is preserved, and thus the re-encryption procedure can be run on untrusted outsourcing server. We prove the virtual black-box security of the obfuscation. The proposed obfuscator can be run on untrusted server to help the perform of the functionality of re-encryption without any sensitive secret revealing.