1. A method of operating a security server to securely transact business between a user and an enterprise via a network, comprising: receiving, at the security server from an enterprise with which the user is currently connected via the network, a request of the enterprise to activate a secure communications channel over the network between the user and the security server, wherein the request includes contact information for contacting the user via other than the network; transmitting, by the security server in response to the received activation request, an activation code for delivery to the user via other than the network and corresponding to the received contact information; receiving, at the security server from the user via the network, an activation code; comparing, at the security server, the received activation code with the transmitted activation code to validate the received activation code; activating the secure communications channel based on the validation of the received activation code, wherein the activated secure communications channel is a channel in which data is encrypted based on the validated received activation code; receiving, at the security server, transaction information including an identifier for identifying the enterprise; generating, at the security server based on the received transaction information, a one-time password for use by the user as a transaction signature, wherein: the one-time-password is generated as a function of the identifier and a secret known only by the security server and the enterprise; and the secret comprises a predetermined value agreed upon by both the security server and the enterprise to be used for generating all additional one-time passwords for all additional users transacting business with the enterprise; transmitting the generated one time password from the security server to the user via the secure communications channel; receiving, by the enterprise, the transmitted one time password to the enterprise from the user; comparing, by the enterprise, the received one time password and a calculated one time password calculated by the enterprise using the secret and the identifier; and transacting, by the enterprise, the business when the comparison is a match.