The present invention relates to a technique which provides a function of compressed encryption large pieces of plaintext information in a single ciphertext in order to improve a space efficiency of the encryption data which occupies most of a storage space to design an efficient SHE technique which is a base of the FHE technique design. More specifically, the present invention relates to a technique which is designed to improve a structure in which only one bit is encrypted/decrypted in the technique of the prior art to encrypt/decrypt multiple bit information to improve the space efficiency for storing a ciphertext.