A system and methods for time and/or location authentication are presented. A hash value is received from a client device and a hash value receiving time of the received hash value is stored. A data block is received after receiving the hash value is received, the received data block comprising alleged transmission signal data. A computed hash value of the received data block is computed, and an estimated transmission signal client receiving time by the client is calculated based on the alleged transmission signal data. A timely possession of the received data block by the client device is authenticated based on a comparison of the computed hash value to the received hash value and a comparison of the hash value receiving time to the estimated transmission signal client receiving time.