Hong Kong Applied Science and Technology Research Institute

Hong Kong Applied Science and Technology Research

Wing Pan Leung

Yiu Wing Wat

Zhibin Lei

Victor Keh Wei Wei

Xiaokang Xiong

A re-encryptor compares hashed digests of updated segments and original segments to located changed segments that must be re-encrypted. A new initialization vector is input to a block cipher engine for each changed segment. Since only changed segments need to be re-encrypted, transmission bandwidth to remote encrypted storage may be reduced. The amount of cipher text that is changed by a single update is reduced to a segment. Segments have a variable length and are bound by bits matching a segment delimiter. Each segment may have many fixed-length blocks that are encrypted by the block cipher engine with the same initialization vector for that segment. The segment delimiter is a randomly-generated word that is included with the initialization vectors in the metadata. Variable-length segments limit update disruption of the cipher text while fixed-length blocks are more efficiently encrypted. Combining segments and blocks provides for better re-encryption of updates.

Partial CipherText updates using variable-length segments delineated by pattern matching and encrypted by fixed-length blocks

A content distribution method with broadcast encryption, comprising an encryption process that includes the computation of a ciphertext using a differential ciphertext generation method. The ciphertext needs to be recomputed whenever the subscriber set changes. The differential ciphertext generation method computes the new ciphertext by reusing previously preserved computational results of a previous ciphertext, thereby improving the efficiency of the system. A content distribution method with broadcast encryption also comprises a decryption process that includes the reconstruction of the encryption secret that is used for decrypting the encrypted content. A wide window point addition method is used in the encryption secret reconstruction. The wide window point addition method reuses previously preserved computational results of group-divided point additions of public parameters, thereby improving the efficiency of the system. A clustering solution with multiple instances of key server and entitlement server allows the expansion of user population in the content distribution network.

System and method for content distribution with broadcast encryption

A content distribution method with broadcast encryption, comprising: executing a setup process, comprising: generating public domain parameters, generating a server secret, and generating one or more client private keys, one for each content receiving client; executing an encryption process, comprising: generating a cipher text using the server secret, a subscriber set, and a randomness, the cipher text being constant and independent of total number of content receiving clients in a distribution network, generating a plain text using the server secret and the randomness, encrypting an original content into an encrypted content using the plain text; distributing the client private keys to the content receiving clients; distributing the cipher text to the content receiving clients; broadcasting the encrypted content through the distribution network; and executing a decryption process on the encrypted content by each of the content receiving clients in the distribution network.

Growing community of inventors

Hong Kong, China

Wing Pan Leung