There are only 21 million bitcoins that can be mined in total. · Once bitcoin miners have unlocked all the bitcoins, the planet's supply will essentially be tapped out. Bitcoin counters the sybil attacks by making use of. PoW based consensus model, in which to verify a transaction the miners have to perform some sort of. Number of Bitcoin (BTC) in circulation as of April 13, How many Bitcoins are in circulation? Since its inception in late , figures for this.