  Cloud computing is considered as the one of the most dominant paradigm in
field of information technology which offers on demand cost effective services
such as Software as a service (SAAS), Infrastructure as a service (IAAS) and
Platform as a service (PAAS).Promising all these services as it is, this cloud
computing paradigm still associates number of challenges such as data security,
abuse of cloud services, malicious insider and cyber-attacks. Among all these
security requirements of cloud computing access control is the one of the
fundamental requirement in order to avoid unauthorized access to a system and
organizational assets. Main purpose of this research is to review the existing
methods of cloud access control models and their variants pros and cons and to
identify further related research directions for developing an improved access
control model for public cloud data storage. We have presented detailed access
control requirement analysis for cloud computing and have identified important
gaps, which are not fulfilled by conventional access control models. As the
outcome of the study we have come up with an improved access control model with
hybrid cryptographic schema and hybrid cloud architecture and practical
implementation of it. We have tested our model for security implications,
performance, functionality and data integrity to prove the validity. We have
used AES and RSA cryptographic algorithms to implement the cryptographic schema
and used public and private cloud to enforce our access control security and
reliability.By validating and testing we have proved that our model can
withstand against most of the cyber attacks in real cloud environment. Hence it
has improved capabilities compared with other previous access control models
that we have reviewed through literature.
