Scheme of standard MIDI files steganography and its evaluation
Daisuke Inoue, Tsutomu Matsumoto · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2002
Steganography aims to make communication invisible by hiding genuine information in innocent objects. We have proposed the SMF steganography that enables to hide information into Standard MIDI Files (SMF). The SMF is widely used as a standard storage format of the data of Musical Instrumental Digital Interface (MIDI). Most of digital musical instruments and personal computers equip the MIDI. Our hiding method utilizes a redundancy of the description of note events (note on/off) in SMF. Some note events, which are performed simultaneously, are allowed as correct contents of SMF even if they are described in any order. Therefore, we can permute the order of such note events according to the embedded data without changing their sounds. To clarify the potential of the SMF steganography, we calculate the embeddable data size about over three hundred SMFs that are opened to the public on the Internet. As a result, the embedding rate, which is the percentage of embeddable data size to cover SMF size, shows about 1% on average, and the best case reaches about 4%. We also clarify the influence of the Quantize function (which adjusts the timing of note events) on the embeddable data size.