Printing 46 billion fake bitcoin BTC$76,387.31-linked tokens on cross-chain application Symbiosis started with a deposit of just 330 satoshi, the smallest unit of bitcoin, worth about 25 cents in total. The service lets users swap tokens across blockchains where they may not originally be supported. A post-mortem published early Tuesday shows how two software flaws in the Symbiosis’ Bitcoin Bridge combined to let an attacker create enormous amounts of syBTC, a token meant to represent bitcoin held by the system.