Proof of presence using machine-readable codes

A server device, comprising:

• one or more processors;
• and
• one or more memories storing computer-executable instructions that, when executed by the one or more processors, cause the server device to perform operations comprising:
• responsive to a request from a terminal device, initiating a data exchange session with the terminal device;
• and
• while in the data exchange session:
• sending, to the terminal device, first information associated with the data exchange session, the first information usable to generate a machine-readable code at the terminal device;
• receiving, from a user device, an indication that the user device has obtained the machine-readable code;
• responsive to the indication, generating a token corresponding to the user device;
• sending, to the terminal device, second information associated with the data exchange session, the second information usable to generate an updated machine-readable code at the terminal device, the second information comprising the token;
• receiving, from the user device, a data exchange request comprising the token;
• and
• validating the token received with the data exchange request.

One or more computer-readable media storing computer-executable instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:

• responsive to a request from a terminal device, initiating a data exchange session with the terminal device;
• and
• while in the data exchange session:
• sending, to the terminal device, first information associated with the data exchange session, the first information usable to generate a machine-readable code at the terminal device;
• receiving, from a user device, an indication that the user device has obtained the machine-readable code;
• responsive to the indication, generating a token corresponding to the user device;
• sending, to the terminal device, second information associated with the data exchange session, the second information usable to generate an updated machine-readable code at the terminal device, the second information comprising the token;
• receiving, from the user device, a data exchange request comprising the token;
• and
• validating the token received with the data exchange request.