After the image-editing techniques developed, anyone is now able to easily edit digital photographs. With the unaided eye it is hard to tell edited digital photos if they are edited or not. Digital photos are losing reliability owing to approachableness, the common characteristic of digital photos. For digital photos to achieve recognition as evidence in court, efforts are being made to find out forged photos. Accordingly, various techniques are being presented internally and externally to detect the fabrication of photos. However, the detection techniques which have been presented so far have limitation in a range of application. This is because they are only applicable when photos are in some particular condition. Once a photograph is fabricated, there remains information in the metadata. One can check whether it is forged or not by analyzing forged information theoretically. However, it is often undetectable as the metadata of photograph is deletable. If the metadata is deleted, one can use various techniques. In the case that the metadata of photograph is intentionally obliterated, one can raise the question of reliability on the photograph.