thank you
Yes exactly our purpose is a crypto app that generates address'es for users for their websites like e-commerce's
but every user needs to withdrawal their balance, for example, I checked this website
coinremitter.com and they generate address' es then the user can withdrawal,
so for withdrawal our back-end should create transactions, is it right?
For withdrawals, the user will generate/provide their own addresses for the funds to be sent. Many sites uses a system called hot wallet whereby the funds are stored in a few addresses that the site controls. The funds will be sent from the individual addresses to the hot wallet and the site would also send the funds from the hot wallet to the withdrawal addresses provided by the user. Depends on how your site functions, you can either give the user the full control of their coins (ie. like they own the whole address) or less control (the owner controls the Bitcoins). This would then be the determining factor as to whether the transactions should be crafted and signed client side or on the server side.