You said: "Then in job after adding package step give same password there and it will be able to get sensitive details including FTP password while executing"
Can you explain how I would do that in the job step, please?
I like your technique better than adding a C# script which is what I used.
Ok..Reading again I understand what you were telling was password that FTP task uses and not ssis package password. In such cases best thing you can do is to use a variable to pass the password to FTP task using expression buolder and then add variable as a configurable item and then pass it through your configurations (either through XML file, SQL server table query or registry/environment variable)
see an example here where I've done it using password passed by user as a config item.