Searchable　Encryption　(SE)　is　an　important　technique　to　guarantee　data　security　and　usability　in　the　cloud　at　the　same　time.　Leveraging　Ciphertext-Policy　Attribute-Based　Encryption　(CP-ABE),　the　Ciphertext-Policy　Attribute-Based　Keyword　Search　(CP-ABKS)　scheme　can　achieve　keyword-based　retrieval　and　fine-grained　access　control　simultaneously.　However,　the　single　attribute　authority　in　existing　CP-ABKS　schemes　is　tasked　with　costly　user　certificate　verification　and　secret　key　distribution.　In　addition,　this　results　in　a　single-point　performance　bottleneck　in　distributed　cloud　systems.　Thus,　in　this　paper,　we　present　a　secure　Multi-authority　CP-ABKS　(MABKS)　system　to　address　such　limitations　and　minimize　the　computation　and　storage　burden　on　resource-limited　devices　in　cloud　systems.　In　addition,　the　MABKS　system　is　extended　to　support　malicious　attribute　authority　tracing　and　attribute　update.　Our　rigorous　security　analysis　shows　that　the　MABKS　system　is　selectively　secure　in　both　selective-matrix　and　selective-attribute　models.　Our　experimental　results　using　real-world　datasets　demonstrate　the　efficiency　and　utility　of　the　MABKS　system　in　practical　applications.　©　2004-2012　IEEE.