Shigeyuki Sakazawa

Arm swing identification method with template update for long term stability

This paper proposes a novel method for biometric identification, based on arm swing motions with a template update in order to improve long term stability. In our previous work, we studied arm swing identification and proposed a basic method to realize a personal identification function on mobile terminals. The method compares the acceleration signals of arm swing motion as individual characteristics, with the tolerant similarity measurement between two arm swing motions via DP-matching, which enables users to unlock a mobile terminal simply by swinging it. However, the method has a problem with long term stability. In other words, the arm swing motions of identical individuals tend to fluctuate among every trial. Furthermore, the difference between the enrolled and trial motions increases over time. Therefore in this paper, we propose an update approach to the enrollment template for DPmatching to solve this problem. We employ an efficient adaptive update method using a minimum route determination algorithm in DP-matching. Identification experiments involving 12 persons over 6 weeks confirm the proposed method achieves a superior equal error rate of 4.0% than the conventional method, which has an equal error rate of 14.7%.

H.264 native video watermarking method

A novel video watermarking method is proposed, which can directly embed a watermark into a bit stream generated by an H.264 video encoder. Watermarking to encoded data provides a content provider of flexible capability to attach secret information; however it brings a drift problem. A drift compensation method has been proposed, however it requires many computations such as DCT and motion compensation. Therefore a new drift compensation method with spatiotemporal watermarking is proposed that only cancels the effect of the embedding on blocks with little motion. It achieves great reduction of computation and realizes fast and high picture quality watermarking. The computer simulation shows that degradation of picture quality is negligible compared to noises due to H.264 compression, and that the proposed method is highly resilient to frequency domain attacks

Light weight MP3 watermarking method for mobile terminals

This paper proposes an MP3 watermarking method that is applicable to a mobile terminal with limited computational resources. Considering that the embedded information is copyright information and metadata, which should be extracted before playing back, the watermark detection process should be executed quickly. However, conventional methods cannot detect a digital watermark at high speed. Thus, this paper proposes that scalefactor values in MP3 data be altered so as not to spoil audio quality. Evaluation tests show that the proposed method is capable of embedding 3bits/frame information and detecting at very high speed without degrading audio quality. Finally, this paper describes an application example of our proposal for authentication with a digital signature.