function setTransferAuthorized(address from, address to, uint expiry) public {
        
        require(transferAuthPermission[msg.sender]);

        
        require(from != 0);

        
        if(expiry > 0) {
            require(expiry > block.timestamp);
            require(expiry <= (block.timestamp + 30 days));
        }

        transferAuthorizations.set(from, to, expiry);
    }