A one-time password may be used and generated using transformation rules. A one-time password transformation rule is received. The one-time password is sent to a user. A response to the one-time password is received. The user is selectively authenticated based on the response corresponding to the one-time password as transformed by the one-time password transformation rule. The one-time password transformation rule may include one or more operations, such as mathematical operations that may be static operations or dynamic operations that change as a function of time. Related systems, devices, methods and computer program products are described.