Avalanche's co-founder helped build a proof-of-work currency six years before Bitcoin... Emin Gün Sirer (@el33th4xor) co-designed Karma at Cornell in 2003 with two of his students. His bios call it the first currency to mint coins through proof-of-work, though Wei Dai's 1998 b-money proposal sketched the idea earlier. Karma aimed to stop freeloading on file-sharing networks by tracking what each user gave and took, long before Bitcoin introduced proof-of-work money. In 2013, he and Ittay Eyal found a flaw in Bitcoin's mining rules. A group of miners could secretly hold back the blocks they found, then release them at the right moment to wipe out rivals' work. Even a minority of miners could earn more than they should. The attack is now known as "selfish mining". He later co-founded @AvaLabs, the company behind Avalanche (@avax), and still runs it as CEO.