An interesting cryptocurrency proof-of-work has emerged that would allow miners to prove their contribution to a DDoS attack against specific servers.
More specifically:
"This proof involves making a large number of TLS connections to a target server, and using cryptographic responses to prove that a large number of connections has been made"
Signatures would be created upon confirmation of TLS connections.
Hackers could then trade DDoS coins for other cryptocurrencies, such as Bitcoin or perhaps Ethereum.
Academics Eric Wustrow and Benjamin VanderSloot who designed this proof-of-work, intend to create a platform that would allow TLS Web servers to be targeted.
You can find their published research here.
The picture below illustrates the cryptocurrency's design: