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In a proxy re-encryption (PRE) system [4], a proxy, authorized by Alice, can convert a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. PRE has found many practical applications requiring delegation. However, it is inadequate to handle scenarios where a fine-grained delegation is demanded. To overcome the limitation of(More)
Certificateless Public Key Cryptography (CL-PKC) has very appealing features, namely it does not require any public key certification (cf. traditional Public Key Cryptography) nor having key escrow problem (cf. Identity-Based Cryptography). However, it does suffer to the Denial-of-Decryption (DoD) Attack called by Liu and Au [1], as its nature is similar to(More)
Cloud computing has drawn much attention from research and industry in recent years. Plenty of enterprises and individuals are outsourcing their data to cloud servers. As those data may contain sensitive information, it should be encrypted before outsourced to cloud servers. In order to ensure that only authorized users can search and further access the(More)
Attribute-based encryption (ABE) is a public-key-based one-to-many encryption that allows users to encrypt and decrypt data based on user attributes. A promising application of ABE is flexible access control of encrypted data stored in the cloud, using access polices and ascribed attributes associated with private keys and ciphertexts. One of the main(More)
At Eurocrypt 2005, Sahai and Waters [7] introduced the concept of attribute-based encryption (ABE). ABE enables public key based one-to-many encryption and is envisioned as a promising cryptographic primitive for realizing scalable and fine-grained access control systems. There are two kinds of ABE schemes [1], key-policy ABE (KP-ABE) and ciphertext-policy(More)