Abstract: A registered provider device encrypts provider input related to a transaction between the provider device and one of many registered user devices to create an encrypted one-time-use provider code (the encryption is performed using an encryption key produced, in part, using a uniquely sequenced number generated by a sequencer maintained by the provider device). Similarly, the user device encrypts user input to create an encrypted one-time-use user code using an encryption key produced, in part, using a uniquely sequenced number generated by a user sequencer maintained by the user device. The provider and user devices independently transmit their different encrypted one-time-use codes to an intermediate entity, which decrypts the encrypted codes. This decryption is performed using one-time-use encryption keys produced using sequencers maintained by the intermediate entity, and this decryption generates an authorization request.