Paying non registered money to owner

Hello ,

I am buying property in Bangalore from OCI ( Overseas Citizenship of India ) , I am paying government property value through online. How i can i pay other money (  Non Registered) to owner) 

For eg : Assume I am buying property for Rs.80 Lakh , government value for property if around 30 Lakh (which i will be paying online/cheque) , how do i pay remaining 50Lakh to owner ??

Any suggestions , appreciated.

Regards

Thanmay