Nowadays, illegal use of multimedia files common happen, although they're already protected with password or something like that. Some people can download passwords to crack the authorization code easily. To avoid that, we have to insert password or label in special ways so it would be difficult for someone to track down the location. In this paper we would like to introduce an algorithm to insert copyright label into audio files, especially audio file with WAVE format.

Label is inserted into frequency domain after raw datas of audio file has been transformed using 2-dimensional Discrete Cosine Transform (DCT). The method which we implemented gives the result that label cannot be detectable by human sense. To make it happen, label contribution to signal quality has to be insignificant.

The DCT process would transform raw datas in such ways, so now we have matrixes which contain datas in frequency domain. These datas are decreasing while frequencies are increasing. From trial, label cannot inserted into high frequencies because someone can easily detect the position of label, then low frequencies are the only choice.

Before label is inserted, label must be encrypted with password to binary sequences. One matrix can only inserted with one bit of label.

Actually, copyright labeling including 3 issues :

1. How to protect unauthorized user to see the file content?
2. How to control file distribution?
3. What about if someone insert another label with same method?

Well, those are difficult questions to answer. The simple answer to the first question is how about we build software that can perform authorization first. With that solution, another problem is appear. There are many software that can play audio files, so we have to make every software in the world are same! That sounds impossible things to do. Then, introducing new format for audio file is the best way.

I have no solution for second question, because since internet is widely used, people can copy easily from anywhere.

For last question, solution is : before the label is inserted, software will check if there label in the file. If label exist already, software will refuse someone for inserting label again.