In some embodiments, an authentication method comprises receiving a request for a digital signature of data from a delegate computer over a secure channel using cryptography to provide authentication, wherein the secure channel comprises at least one wireless communications link; displaying information derived from the data; prompting a user for approval of the request with information derived from the data; in response to receiving approval from the user, creating the digital signature of the data using one or more private keys stored in a key enclave; and sending the digital signature to the delegate computer over the secure channel.