Publications

Abstract : The amount of data rapidly increases every year. Hence, there is a need for a new generation of techniques and tools to assist humans in storing and to share these voluminous amounts of data with others securely. Data sharing is an important functionality in cloud storage besides the convenience of not having to buy software programs and install them on your own servers, using cloud applications instead can be cheaper. Public-key cryptosystems that produce constant-size ciphertexts that provides efficient delegation to decrypt any set of ciphertexts provided with a secure key for authorized users. The originality is that one can aggregate any set of secret keys and make them as compact as a single key, which includes the power of all the keys being aggregated. The secret key holder can use a constant-size aggregate key for flexible choices of ciphertext set in cloud storage, but the other files that are encrypted outside the ciphertext set remain confidential. This aggregate key can be conveniently sent to others or be stored in a smart card which has a very limited storage as the key size is constant.