Suppose I have n subordinates at work. Any subordinate should be able to submit his or her report anonymously to me via digital means.
Also suppose that I have no means of broadcasting any form of information securely to my subordinates. That is - any message I broadcast to my subordinates should be able to be sniffed by an eavesdropper. I am also not able to communicate directly (unicast) one-on-one with my subordinates.
Is there any way to develop a protocol for my subordinates to submit their report while preventing (or identify) attackers (that are not any of my subordinates) forging a report that could also be submitted to me?
There are no other assumptions other than those bolded and I should be free to make any other assumptions as needed.
What I've got so far:
- Any public key exchange system - Each of my subordinates broadcast their public key which I can use to verify their signature of the message. The problem with this is that it is not anonymous. Each subordinate can be identified using the unique public key once published.