Mobile computing devices have been developed to increase the functionality that is made available to users in a mobile setting. For example, a user may interact with a mobile phone, tablet computer, or other mobile computing device to check email, surf the web, compose texts, interact with applications, and so on. One challenge that faces developers of mobile computing devices is efficient power management and extension of battery life. For instance, a host device may supply an accessory device with power and/or draw power from an accessory device in different scenarios. However, enabling a device to give/receive power to any connected accessory device (e.g., an unauthorized device) may reduce battery life in unexpected ways and/or may be inefficient and even dangerous if power transfers are allowed to occur indiscriminately.