Encryption apparatus, method for encryption, method for decryption and computer-readable recording medium

An encryption method, comprising,

• generating an increasing function parameter regarding a predetermined one-way increasing function and a secret key necessary for encryption;
• generating a first order-preserving encryption area regarding a plaintext using the one-way increasing function where the increasing function parameter is applied;
• generating a second encryption area regarding the plaintext using the secret key;
• and
• generating a ciphertext by concatenating the generated first encryption area and the generated second encryption area.

A computer readable recording medium which includes a program for executing an encryption method, wherein the encryption method comprises:

• receiving an increasing function parameter regarding a predetermined one-way increasing function and a secret key necessary for encryption;
• and
• generating a first order-preserving encryption area regarding a plaintext using the one-way increasing function where the increasing function parameter is applied;
• generating a second encryption area regarding the plaintext using the secret key;
• and
• generating a ciphertext by concatenating the generated first encryption area and the generated second encryption area.

An encryption method, comprising,

• generating a first order-preserving encryption area regarding a plaintext using a predetermined one-way increasing function;
• generating a second encryption area regarding the plaintext using a secret key;
• and
• generating a ciphertext by concatenating the generated first encryption area and the generated second encryption area.