A machine implemented method for protecting a target domain and a source domain from unauthorized accesses. The method comprising: identifying an exit call gateway comprising an exit transition instruction and at least one exit access parameter, said exit access parameters restricting exit from said source domain; identifying an entry call gateway corresponding to said exit call gateway, said entry call gateway comprising a transition instruction and at least one entry access parameter, said entry access parameters restricting access to said target domain; determining that said exit access parameters and said entry access parameters are compatible with each other; and performing a context switch from said source domain to said target domain, when said exit access parameters and said entry access parameters are complied with.