Development of Wavelet Domain Multi-Dimensional Adaptive Filter and Its Application to On-line Signature Verification

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The purpose of this research is to improve ability of on-line signature verification by introducing of the time-frequency analysis based on the wavelet transform. The results were as follows:1. Daubechies' mother wavelet is suitable for the analysis.2. Normalization of the data sample is necessary for independence of the input.3. Stroke matching based on the dynamic programming (DP) method between the input data and reference one at each level is introduced.4. When the difference of the number of the strokes within +__-2, the input is treated as a candidate of the genuine.5. Reference data is produced by an average of five genuine data at each level.6. Fluctuation of the amplitude at levels from 1 to 4 is very large, so that it is not suitable for verification.7. Fluctuation of the amplitude at levels from 9 to 10 is quite small, so that is not suitable for verification, either.8. For speed-up of convergence, the normalization of the step size in the adaptive algorithm is required.9. A simple verification method based on the value of convergence, that is, the adaptive weight converges on 1 if the signature is of the genuine. Otherwise, it converges on 0, is achieved.10. Total verification is achieved based on whether an average of the converged values of the upper 4 levels is larger than the threshold value or not.As a result, we obtained 92% recognition rate when the threshold was 0.2.