Table-6: Available Key Sizes

Key Size

Relative Security Level

512 or 768

Not regarded as secure.

1024 or 2048

Secure.

3072 or 4096

Very secure.

Note about key sizes: Typically, certificate authorities use key sizes of 1024 or 2048. When certificate owners wish to keep their keys for a longer duration, they choose 3072 or 4096 bit keys.