As cryptocurrencies explode in popularity, employers are clamoring for workers with expertise in the emerging field. From a report: Demand for online freelancers who specialize in blockchain and bitcoin-related work surged last quarter, according to data compiled by Upwork, a website that connects freelancers with employers. The two skills were respectively the second and third fastest-growing skills on Upwork's platform. With the price of bitcoin having surged more than 500 percent this year, companies are rushing in to capitalize on the boom. Other skills in Upwork's list of fastest-growing skills include robotics (No. 1), as well as a cybersecurity specialty called penetration testing (No. 4) and a subfield in artificial intelligence called deep learning (No. 8).