SSIS Package Security I am writing a Package for one of my client according to his requirements. Package development is totally complete now time is to protect it with some security.
Is this possible I encrypt all the data with password so no one can open package file(.dtsx) ? and when some one want to execute package he require some other password instead of which I used to protect package file.
This is not native functionality. You can encrypt: Nothing, Sensitive items, Everything. There is no capability to assign one key for development and one for execution. 

Instead, the way to restrict execution is through proper security, which is never the last item. If the SSIS package is loading a database, you ensure that only the correct user(s) can do connect/write to the database. If you store the packages in the database, deny them the ability to run the packages. If it's on the file system, set the proper ACL so they can not get to them.