What will be Best Approach for E-sign functionality?

why? Perhaps you can clearify that this. :) I really struggle to understand the idea behind this request.
Tasks are assigned to a specific user or group of users, which need to pull it to work on it. So it is pretty clear who is working on it at a specific moment in time. Why do you want to sign it on top? The moment the task is submitted, we often store who submitted it at step xyz. Could be that sufficient?