1. A method for a first computing device to make authentication information available to a second computing device, the method comprising: creating authentication information, the authentication information including content data, a public key of the first computing device, a network address of the first computing device, and a digital signature, the network address having a portion derived from the public key of the first computing device, the digital signature generated by signing with a private key of the first computing device corresponding to the public key, the digital signature generated from data in the set: the content data, a hash value of data including the content data; and making the authentication information available to the second computing device, in part by sending a message to the second computing device, the message including the digital signature in a packet option.