No problem Farhan 
. I'm just trying to help you, SCN helps me so much, now time to payback.
So Shabarish Vijayakumar he is a legend, he nows about digital signatures.
Also Vladimir Balko do you any idea about what kind of digital signature format you must use for that ?
Do you have a document of requirement from Bank ?
Welcome Farhan !!
Regards,
Ricardo Viana.