https://www.bleepingcomputer.com/news/security/over-435k-security-certs-can-be-compromised-with-less-than-3-000/

After analyzing millions of RSA keys and certificates generated on low entropy lightweight IoT devices, security researchers at Keyfactor discovered that more than 435,000 of them shared their prime factors making it easy to derive their private key and compromise them.

RSA keys are derived from random prime numbers (prime factors) and are used to securely transfer data to a remote source by encrypting it with the publicly available key, a process that only allows the remote source to decrypt the information using a private key.