Abstract-A perceptible removable watermark can be used to add copyright owner's identification to media or lower the value of the digital contents. The application scenario for perceptible watermarks is to give the protected contents available freely for download as a preview. For a fee, the watermark can be removed to restore the media quality to the original level. We present a scheme to protect the audio data by embedding high capacity robust watermark to it. The watermark can be removed using a secret watermarking key with only minimal remaining distortion. The protection watermark embedding and detection is done in the spectral domain. The watermark is embedded into selected FFT coefficients' magnitudes of the cover audio using frequency hopping method. The method proposed is media format independent and it can be used with lossy compression. The objective and subjective quality evaluations indicate that the audio quality after watermark removal is excellent.

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Abstract-Digital watermarking is a method to embed secret data into digital signals. We present a novel service that uses watermarking to add metadata into radio broadcast music. A user can record the music from radio loudspeakers and extract the watermark. The watermark can contain e.g. value adding metadata about the song or a link to an external server. This solution offers a new channel for mobile commerce.

This paper describes a counter scheme that uses hash functions to count how many times the user is allowed to play protected content in a DRM-enabled player. The proposed basic scheme can be used in scenarios where the user cannot be assumed to have online connection. We discuss the weaknesses of the proposed scheme and present alternative to the basic scheme, which increases the security of the counter.

Abstract-Digital watermarking is a method for embedding secret data into digital signals. We present a novel service that uses watermarking to add metadata into radio broadcast music. A user can record the music with a mobile phone from radio loudspeakers and extract the watermark. The watermark can contain, for example value adding metadata about the song or a link to an external server that can provide the user a possibility to buy a CD with the song in question, or a ticket to the artist's next concert. This solution offers a new channel for mobile commerce. The method is tested against sampling rate changes and DA/AD conversion in noisy environment, where the audio is played through loudspeakers and recorded using a mobile phone. The success ratio of the message extraction was 83 % in the experiments, while the subjective quality was graded on average as perceptible but not annoying. IndexTerms-audio watermarking, multiple watermarking, frequency hopping, spread spectrum, DA/AD