User validation for mobile telephones

A combination of text-independent speaker verification and user profiling as a new biometric for crime prevention on mobile telephones is proposed, The verification carried out on the speech throughout the call hence obviates the need for direct user involvement while providing high impostor rejection. Low user rejection is achieved by monitoring the pattern of numbers called. While the pattern is substantially unchanged the speaker verification threshold is low minimising the level of false rejections. The threshold is raised if the calling pattern deviates from the normal. Analysis of a limited number of user call records shows that the users tend to call a small set of numbers repetitively and that deviation from this pattern are infrequent. Tests of a Gaussian mixture model based speaker verification system on an appropriate database gave an equal error rate of 4% showing that a text independent system can approach the performance of a text dependent system.