There are two types of SSL certificates, one is ECC certificate (built-in ECDSA public key), and the other is RSA certificate (built-in RSA public key). ECC is more secure than RSA of the same length, which means that under the same security conditions, the key length of ECC is much shorter than that of RSA, and encryption and decryption will be faster. The following is how to apply for a TSL/SSL certificate on a Linux server using the acme.sh script.