OneKey founder Yishi outlined personal security recommendations for converting an iPhone into a cold wallet, advising users to utilize an iPhone 17 or newer running iOS 27 or later. He further suggested replacing the device every one to two years to maintain optimal security standards for self-custody. Yishi emphasized that this guidance represents a personal security recommendation rather than an official Apple certification or guarantee. He warned that even when older devices are kept offline, the risk of unauthorized physical access cannot be entirely eliminated, underscoring the importance of using newer hardware for storing digital assets.