The University of SydneyPage 25Constructing a block–Smaller the threshold it is more difficult to find a nonce.–Equivalent to how many zeros are at the beginning of resulting 256 bit hash ?–Bitcoin difficulty is adjusted every 2016 blocks (2 weeks) to keep 10 minute block interval.–Every full node adjust difficulty level by;–New difficulty = old difficulty * (actual time of last 2016 blocks/20160 minutes)–Note: theoretically new difficulty can go up or down.