Abstract
Cloud computing provides the capability to use computing and storage resources on a rented basis and reduce the investments in an organisation's computing infrastructure. With all its benefits, cloud computing also brings with it concerns about the security and privacy of information extant on the cloud as a result of its size, structure, and geographical dispersion. Secure communication in cloud environment is necessary to access remote resources in a controlled and efficient way. For validation and authentication digital signatures using public key cryptography is extensively used in cloud computing. Further to keep confidentiality, digital envelope which is the combination of the encrypted message and signature with the encrypted symmetric key is also used. In this paper we propose a timestamp-based authentication scheme for cloud client with a modified digital envelope. As hyperelliptic curve cryptosystem (HECC) is known for its small key size and high security, we have taken HECC encryption technique. We have also presented a security analysis to show that our scheme can resist various attacks related to cloud environment.