Developing an electronic signature addin for Word

Question

Hello all,

My customer is unhappy with the electronic signature widget in Word, and I am looking into the possibility of developing an alternative using a Word addin. The electronic signature addin would need to be able to interact with the user's certificate stored on a smart card. I notice this functionality is currently handled by the existing electronic signature widget, though it appears to be some sort of integration between Microsoft Word and Windows Security. Does anyone have any experience with developing addins that leveraged signatures, smart card credentials.. or would otherwise be able to offer advice or examples for implementing eSignature in Word? Any help would be greatly appreciated. Thanks!