It is simpler to manage an electronic signature on a It is simpler to manage an electronic signature on a server. On the contrary, authentication in a paper is more conveniently managed by a serverless system. However, data embedded in a document relies on an authentication system and security system. In view of this, a security data extraction unit separates electronic data into security data and non-security data. An image arrangement unit arranges the non-security data on a paper surface and converts it to readable image data. An encryption processing unit encrypts the security data. An authentication program generation unit generates an authentication program that executes authentication using authentication data. A package unit packages the encrypted data and the authentication program. A background embedding unit generates background image data where the package data is embedded in a background pattern. An output image generation unit synthesizes the background image data with the readable image data, and generates encrypted image data.