In a system for performing an action regarding an account in response to an electronic communication received from a sender by a receiver, wherein the electronic communication includes sender identity information associated with the account and a digital signature derived using a private key of a public-private key pair, and wherein the public key of the pair has been associated with the account by the receiver such that the public key is retrievable based on the sender identity information, a method of validating the identity of the sender for the electronic communication includes: (a) retrieving the public key based on the received sender identity information; and (b) comparing a function of the public key and the digital signature with a function of the electronic message. The digital signature is derived from an electronic message possessed first by the sender before the receiver. The sender identity information may be different from the electronic message.