Systems, methods, and computer program products for secure optimistic mechanisms for constrained devices

Embodiments of the invention may provide for systems and methods for secure authentication. The systems and methods may include receiving, by a constrained device, a random string transmitted from a server; determining, by the constrained device, a responsive output by evaluating a first deterministic function based upon the received random string, a locally generated string and a first private key stored on the constrained device; and transmitting at least one portion of the responsive output and the locally generated string from the constrained device to a server. The systems and methods may also include determining, by the server, a validation output by evaluating a second deterministic function based upon the random string, the locally generated string, and a second private key of a plurality of private keys stored on the server; and authenticating the constrained device based upon the server matching the transmitted at least one portion of the responsive output to at least a portion of the validation output.