Emergency Button: Evacuation of Crypto Asset When Key Loss

We discuss countermeasures against the loss of private keys in crypto assets. Since the private key is necessary to sign transactions when transferring crypto assets, the loss of the private key causes the loss of the corresponding crypto assets. In this paper, we propose a concept and the implementation of "Emergency Button" as a countermeasure against key loss. In our proposed method, a smart contract as "Emergency Button" is generated in advance to evacuate crypto assets corresponding to a private key to another account. When the key is lost, the owner of the crypto asset activates the emergency button and the crypto assets are moved to another account. Owner can use the private key of the other account instead of the lost key. One of the advantages of our proposed method is that the owner can immediately take the action, namely push the emergency button when he or she notices the loss of a key.