In the Harry Potter universe, there\u2019s a handy spell for when you need to stop someone from spilling your secret plans or shit-talking during a duel. It\u2019s called Mimblewimble, otherwise known as the tongue-tying curse. It\u2019s also the name of a privacy technology designed for cryptocurrencies\u2014because, well, somebody\u2019s gotta keep crypto weird. The first coins to use Mimblewimble\u2014distinct efforts called Grin and Beam\u2014both launched in January.