Data　confidentiality,　a　fundamental　security　element　for　dependable　cloud　storage,　has　been　drawing　widespread　concern.　Public-key　encryption　with　keyword　search　(PEKS)　has　emerged　as　a　promising　approach　for　privacy　protection　while　enabling　efficient　retrieval　of　encrypted　data.　One　of　the　typical　applications　of　PEKS　is　searching　sensitive　electronic　medical　records　(EMR)　in　healthcare　clouds.　However,　many　traditional　countermeasures　fall　short　of　balancing　privacy　protection　with　search　efficiency,　and　they　often　fail　to　support　multi-user　EMR　sharing.　To　resolve　these　challenges,　we　propose　a　novel　lightweight　multi-user　public-key　authenticated　encryption　scheme　with　keyword　search　(LM-PAEKS).　Our　design　effectively　counters　the　inside　keyword　guessing　attack　(IKGA)　while　maintaining　the　sizes　of　ciphertext　and　trapdoor　constant　in　multi-user　scenarios.　The　novelty　of　our　approach　relies　on　introducing　a　dedicated　receiver　server　that　skillfully　transforms　the　complex　many-to-many　relationship　between　senders　and　receivers　into　a　streamlined　one-to-one　relationship.　This　transformation　prevents　the　sizes　of　ciphertext　and　trapdoor　from　scaling　linearly　with　the　number　of　participants.　Our　approach　ensures　ciphertext　indistinguishability　and　trapdoor　privacy　while　avoiding　bilinear　pairing　operations　on　the　client　side.　Comparative　performance　analysis　demonstrates　that　LM-PAEKS　features　significant　computational　efficiency　while　meeting　higher　security　requirements,　positioning　it　as　a　robust　alternative　to　existing　solutions.　©　2005-2012　IEEE.