Patent ID: 8380720

Claim:
A method for data encryption and conjunctive keyword search of encrypted data, the method comprising: generating a secret key for data encryption and a secret key for index generation of encrypted data; encrypting data to be stored in a server for data storage using the secret keys for data encryption; including a plurality of keyword fields and extracting the plurality of keywords from the data, and storing them in the plurality of keyword fields, respectively; generating indexes for the encrypted data using address information on the keyword fields in which the keywords extracted from the data are stored and the secreted key for index generation; selecting search keywords for encrypted data search; confirming keyword field addresses stored with the selected search keywords among the keyword fields in which each keyword for the encrypted data is stored; generating trapdoors for the search keywords using the secret key for index generation used to generate the indexes for the encrypted data; and transmitting the generated trapdoors and the keyword field addresses confirmed in the confirming the keyword field addresses to the server for data storage, wherein the indexes include index identifiers which are used as values for comparison keys to confirm whether the indexes include index values corresponding to the search keywords, wherein the generating the trapdoors generates the trapdoors by calculating an inverse element of the secret value φ(n) that satisfies φ(n)=(p−1)·(q−1) from the secret values p and q used for generating the indexes for the encrypted data, wherein the generating the trapdoors generates the trapdoors by summing the values hashing the plurality of search keywords using the secret key for index generation.