Apple has added a warning when you plug an unauthorized charge / sync Lightning cable into your iPhone 5. The popup message states “This cable or accessory is not certified and may not work reliably with this iPhone.”
Unauthorized Lightning cables and docks quickly entered the market after the new connector standard was introduced in the iPhone 5, driven by shortages of Apple's official Lightning cables and slow progress in bringing official third-party manufacturers on board. Availability of certified Lightning cables and accessories has since broaden significantly through Apple's MFi Program, but unauthorized parts remain on the market.
Apple's Lightning connectors use several chips to manage dynamic pin assignment for the diminutive connector, chips which also allow Apple to recognize whether the connectors come from authorized channels.