Cryptocurrencies are digital assets, alternative investments held by an estimated 500 million people worldwide. In time, it will be common for nearly everyone on the planet to possess other types of digital assets, including medical history, identity credentials and smart contracts. What is common between crypto and other digital assets is the need for owners to maintain secure custody of critical data, including accessing, managing and possibly recovery. Cold storage wallet technology, which is based on storing data encryption keys offline, is currently used to provide self-custody of cryp...