Darkcoin is an open source peer-to-peer cryptocurrency that uses a system called Darksend to add privacy to transactions. Darkcoin uses a chained hashing algorithm approach called X11 for the proof-of-work. Instead of using the Secure Hash Algorithm (SHA) 256 or scrypt it uses 11 rounds of different hashing functions. With chained hashing, high end CPUs give an average return similar to that of GPUs. Another side effect of the algorithm is that GPUs run at about 30% less wattage than scrypt and 30% to 50% cooler, putting less stress on the computing setup and ensuring lower energy bills for miners.