TLS, SSL Certificate

This post analyzes TLS, SSL Certificates.

1. Certificate Classification by Domain Coverage

Certificates are classified as follows according to the range of Domains they apply to.

1.1. Single Domain

A certificate that can be used for only one single Domain.

• aaa.ssup2.com
• bbb.ssup2.com

1.2. Multi (SAN) Domain

A certificate that can be used for one primary Domain and multiple additional Domains.

• aaa.ssup2.com (primary) + bbb.ssup2.com (additional 1) + ccc.ssup2.com (additional 2)

1.3. Wildcard Domain

As the name implies, it contains the Wildcard (*) character and refers to a certificate that can be used for multiple Subdomains under one Domain or Subdomain. It is classified as an n-th level certificate depending on the position of the Wildcard.

• *.ssup2.com / 2nd level
  • ssup2.com
  • aaa.ssup2.com
  • bbb.ssup2.com
• *.blog.ssup2.com / 3rd level
  • blog.ssup2.com
  • aaa.blog.ssup2.com
  • bbb.blog.ssup2.com

1.4. Multi Wildcard Domain

A certificate that can be used for multiple Subdomains under multiple Domains or multiple Subdomains.

• *.blog.ssup2.com + *.git.ssup2.com
  • blog.ssup2.com
  • aaa.blog.ssup2.com
  • git.ssup2.com
  • aaa.git.ssup2.com

2. References

• Types of SSL/TLS Certificates : https://eunhyee.tistory.com/228
• What is a Multi-Domain (SAN) Certificate? : https://knowledge.digicert.com/solution/SO9440.html
• How to Choose the Right Type of TLS/SSL Certificate : https://www.digicert.com/blog/how-to-choose-the-right-type-of-tls-ssl-certificate