A wireless device can obtain a network information record from another device operating as a credential source. The network information record can include network access information for a wireless network (e.g., SSID and password) and a usage policy specifying conditions under which the wireless device should search for the wireless network (e.g., temporal and/or spatial conditions). The wireless device can implement the usage policy by searching for the wireless network only when the conditions are satisfied. In some instances, the network access information can include instructions for dynamically generating time-varying network access information, and the wireless device can use the instructions to generate network access information during a search for wireless networks.