Systems, computer program products and methods for authentication using a one-time password. In system that includes a client, a service provider, and an authentication service, the authentication service generates an authentication service identifier for the client. Any suitable identifier may be used for the authentication service identifier, which generally takes the form of an arbitrary number of characters. From the client, the authentication service receives a client moniker (e.g., a username) for the client to use when accessing the authentication service. The authentication service sends a one-time password to the client for the client to use in accessing the service provider. When the authentication service receives a one-time password from the service provider, the authentication service sends the authentication service identifier for the client to the service provider to authenticate the client if the one-time password received from the service provider matches the one-time password sent to the client.