Methods for enabling secure online transactions using a mobile device are described. A mobile device may capture an image associated with a banking card in order to generate checkout information and to automatically populate checkout fields with the checkout information prior to completing an online transaction. In some cases, the mobile device may be used to select items to be purchased from an online merchant, access a checkout page of the online merchant for purchasing the selected items, acquire an image that encodes checkout information, acquire a personal code associated with an end user of the mobile device, generate the checkout information using the acquired image and the personal code, automatically populate one or more fields associated with the checkout page with the checkout information, delete the checkout information from the mobile device, and submit the checkout information to complete the purchase of the selected items.