The major aim is to build certified secure systems with respect to information flow. RWFM ( readers writers flow model) is a model developed by us towards decentralised inflow flow security. RWFM is a robust decentralised model that has declassification operations and is complete with respect to Denning’s lattice. Using this model, we have proposed/built (i) Information Flow Secure Linux, (ii) A language based security platform for guaranteeing information flow security of programs, (iii) a sound semantics for non-interference freedom, (iv) generalisation of information flow security for concurrent programs, (v) security certification of SPARK Programs, (vi) information flow analysis for ABAC ( attribute access control) (vii) application for privacy preserving Hadoop etc.We have also been working on security assessment blockchain systems and arriving at guidelines for a practitioner, developing a platform for vulnerability analysis of smart contracts in Solidity and analysis of privacy