SHA1 Hash Collision
Its really windy, so windy that this plane couldn't land first try:
It’s windy today: here’s 500 tons of super-jumbo going wobble on the wing! https://t.co/VGjfOctkqg
— Charlie Stross (@cstross) February 23, 2017
Google found a SHA1 Collision their blog post is much smarter than anything I could write about it.
Reading: Babylon's Ashes, Diamond Age