Cryptographic participant vouching

A method comprising:

• receiving, by a third device and from a first device attempting to join a group communication session, a voucher data item for joining the group communication session between the third device and at least a second device, the group communication session including an exchange of audio data or video data between the second device and at least the third device, wherein the voucher data item is signed by the second device and includes first participant information obtained through participation of the second device in the group communication session;
• retrieving, by the third device, a key associated with the second device;
• obtaining, by the third device and through participation in the group communication session, second participant information associated with the participation of the second device in the group communication session;
• and
• verifying, by the third device, the voucher data item from the first device based on the key and a comparison of the first participant information obtained through participation of the second device in the group communication session and the second participant information obtained through participation of the third device in the group communication session to verify that the second device has vouched for the first device to join the group communication session.

A non-transitory computer-readable medium comprising computer-readable instructions that, when executed by a processor, cause the processor to perform one or more operations comprising:

• receiving, by a first device, a voucher data item, from a second device that is participating in a group communication session with at least a third device, wherein the voucher data item is received prior to participation of the first device in the group communication session with at least the third device, the group communication session including an exchange of audio data or video data between the second device and at least the third device, wherein:
• the voucher data item includes participant information obtained through participation of the second device in the group communication session, and
• the voucher data item is signed with a key associated with the second device;
• and
• providing the voucher data item to at least the third device to verify that the first device is vouched for by the second device for participation in the group communication session.