Security concerns over inadvertent data leaks in the cloud may greatly ease the capability of selectively sharing encrypted data with different users via public cloud storage. So designing such an encryption schemes is a key challenge which lies in the efficient management of encryption keys. When any group of selected documents need to share with any group of users a desired flexibility is required with demands different encryption keys, which are used for different documents. However this also indicates the need of securely sharing to users a large number of keys for encryption and search, and those users will have to safely save the received keys, and submit an equally large number of keywords trapdoors to the cloud in order to perform search over the shared data. The indicated purpose of safe communication, storage, and difficultly clearly renders the approach impractical. In this paper, we address this practical problem, which is greatly neglected in the literature, here we are proposing the new concept of key aggregate searchable encryption and instantiating the concept through a concrete KASE scheme. In this scheme, the documents are shared by just submitting a single trapdoor by the user to the cloud for querying and this single key is being received by the data owner for sharing large number of documents. Our proposed scheme can confirm prove both the safety as well as practically efficient channels by security analysis and performance evaluation. It can securely store and manage the users in their devices. In order to perform a keyword search over many files a large number of trapdoors must be generated by users and submitted to the cloud. Such a system with secure communication, storage and computational complexity may lead to inefficiency and impracticality.