A method of authenticating an entity by a receiving party with respect to an electronic communication that is received by the receiving party and that includes both a unique identifier associated with an account maintained by the receiving party and a digital signature for a message regarding the account, consists of the steps of, before receipt of the electronic communication, first associating by the receiving party a public key of a public-private key pair with the unique identifier and, thereafter, only conducting message authentication using the digital signature received by the receiving party in the electronic communication and the public key associated with the account identifier.