Methods and Systems for Verifying a Source of a Message or Call

Various implementations described herein are directed to providing time-dependent authentication of a sending device. A message to a designated receiver is prepared. A portion of at least one secret identifier value of the sending device is retrieved. A portion of time information is retrieved. An authentication field is produced using the portion of the at least one secret identifier value and the portion of the time information. The authentication field is attached to the message. The message is transmitted to the designated receiver.