Is it safe to transfer/pledge our shares to our broker for margin money?

We need some extra money to trade option selling thinking about transferring some shares from demat to our broker.

Once we transfer to client collateral account (CCA) broker than re-pledge to NBFC to give margin money?> I mean how does it work ?
or broker gives margin money from his own funds? How much interest they charge or they don't charge anything?

We have CDSL easiest facility ...there is a option to pledge from there it same as traditional pledge? is it safer to use CDSL route for pledge?

We have heard some scam news where brokers misuse clients shares/trust that is why I am worried before pledging with a broker.

Please advise..thanks.