A security certificate authority from India had several of their keys deciphered because the numbers used to generate them were way too short. In fact one of them was simply the number 4. Because of this basically the entire internet has been put at risk because it’s trivially easy to forge keys from this trusted authority.

https://www.theregister.com/security/2026/10/20/indian-certification-authority-emudhras-private-keys-compromised-one-of-them-was-the-number-4/5304312