Device for ciphertext index and search and method thereof

The invention provides a device for ciphertext index and search and a method thereof. A multilevel ciphertext index is created for a ciphertext. The primary index entry comprises a primary index entry identifier and a ciphertex of the primary index information of each related file. Each primary index information comprises an identifier of the related secondary index entry and decryption information. The secondary index entry comprises a secondary index entry identifier and ciphertex of the secondary index information. The information required by acquiring the file is included in the secondary index information. Through decrypting information through the secondary index information in the decrypted primary index information, the ciphertex of the related secondary index information can be decrypted to obtain the information of file decryption key and the like.