Dynamically generated quick response (QR) codes are used for secure communication to/from mobile devices. In one example, a QR code identifies a product or service selected by a user using a mobile device. The mobile device generates the QR code identifying the user's selection, and displays the QR code for reading by a retail kiosk. The retail kiosk, such as movie-rental kiosk, extracts the product or service selection encoded in QR code and provides the identified product or service to the user. The QR code can additionally identify a user account, such that payment for the product or service is automatically charged to the account identified from the QR code. In another example, the QR code is used to transfer money and/or credits between a user and a retailer, or between two users.