https://scotthelme.co.uk/eight-bits-of-trust-emudhras-ca-keys-cracked-in-milliseconds/
"One of eMudhra's certificate authority private keys is the number 4.
Not a number that starts with 4, or the number 4 followed by a few hundred random digits, just, 4... Another one is 56, and another is 115. I know, because I recovered all of them from their public certificates on my laptop just now, and it took less than a second."