Transactions are deemed safe after ten confirmations, meaning that trans- actions are permanent in less than 14 minutes. Originally Bitcoins were mined using the central processing unit CPU of a typical desktop computer. For an in-depth analysis of the mathematics and probabilities related to Nxt block forging, see mthcls paper, The math of Nxt forging, which is located at http: What's new. Cumulative Difficulty. Since the full token supply already exists, Nxt is redistributed through the inclusion of transaction fees which are awarded to an account when it successfully creates a block. Since this algorithm has not yet completely been implemented, and because its implications on the Nxt network are significant, it will be outlined in a separate paper. All blocks contain the following parameters:. Four years later in January , the size of the Bitcoin blockchain stood at 4 gigabytes GB about the amount of data required to store a two hour movie on a DVD disk. All Nxt transactions are considered unconfirmed until they are included in a valid network block. The last point is significant.