Ethereum Cookbook

How to do it…

1. Every DApp is authenticated and authorized by the user's address. The address is the key to accessing a decentralized application built on Ethereum. 
2. Consider the example of CryptoKitties, a popular crypto collectable game built on Ethereum. The application identifies the user using their Ethereum address. A user can purchase kitties using their address and the ownership of the asset will be transferred to them.
3. The application lists all the kitties owned by the currently logged in address on a different page. You can easily track the assets using the address:

mapping(address => uint[]) kitties;function getKitties(address _owner) returns(uint[]) {    return kitties[_owner];}

4. Any tasks involving the kitties can only be performed ...