This was a mainstream idea when I was in CS school 12 years ago. There are creative alternatives too, eg. by requiring the client to complete a network scavenge

This was a mainstream idea when I was in CS school 12 years ago. There are creative alternatives too, eg. by requiring the client to complete a network scavenger hunt: https://people.cs.pitt.edu/~adamlee/pubs/2012/abliz2012ijas.pdf https://people.cs.pitt.edu/~adamlee/pubs/2012/abliz2012ijas....