What is Digital Certificate? – Types of Digital Certificates

Digital Certificate is a set of electronic credentials that are used to verify the certificate owner’s identity through encryption keys (public and private key). These keys digitally encrypt and signs information. A digital certificate ensures that the certificate contains a public key that belongs to the SSL requestor to which the certificate was given. A certificate authority issues a Digital certificate.

What is Digital Certificate?

A digital certificate contains two keys like a public key and a private key. A public key resides in a certificate while the private key is with the recipient. A message encrypted with a public key can only be decrypted with a private key. When a certificate authority issues a certificate, it includes encryption algorithms, digital signature, serial number, expiry dates, name of a certificate owner.

The certificate issuance process starts with submitting the CSR (certificate signing request) and submission of the required information. Once the information is submitted, domain ownership is verified along with business registration documents (if required). After verification, the certificate authority issues a digital certificate that needs to be installed on the server.

Types of Digital Certificates:

TLS/SSL certificate:

TLS/SSL certificate is installed on the server to encrypt the information that travels between the server and the browser. The server can be any type of server like LDAP server, web, app, or mail server on which authentication is needed for encrypting and decrypting the data. When a TLS certificate is on the website, the URL will start with HTTPS instead of plaintext HTTP. TLS certificates can be of different types like single domain, multi domain, wildcard SSL, multi domain wildcard SSL.

Single Domain SSL: Single domain SSL only secures a single domain/subdomain with strong encryption. It is available at an affordable price and can be ideal for blogs, forums, and single domain websites. This certificate covers www and non-www versions, for example, www.domain.com and domain.com.

Multi Domain SSL: Multi domain SSL aka SAN SSL certificate can secure multiple domains and subdomains at a very nominal price and this certificate can be installed on multiple servers. The certificate has the ability to safeguard up to 250 domains (depends on the provider). Below is an example of a multi domain SSL certificate.

  • www.domain1.com
  • blog.domain.com
  • mail.domain2.com
  • payment.subdomain1.domain2.com

Wildcard SSL: Wildcard SSL certificate is ideally for the protection of the first level of subdomains related to a primary domain. All subdomains will have the same level of encryption (SHA-2) as per the CAB/forum standards. You can add an unlimited number of subdomains to the wildcard SSL certificate without spending any extra penny. You can check the below example of wildcard SSL.

  • *.domain2.com (Primary domain)
  • blog.domain2.com (subdomain)
  • mail.domain2.com (subdomain)
  • payment.domain2.com (subdomain)
  • autodiscover.domain2.com (subdomain)

Multi Domain Wildcard SSL: Multi domain wildcard certificate is an ideal way to secure different levels of wildcard domains and subdomains, which are needed to be secure with robust encryption. A single wildcard SSL can secure one primary domain and subdomains but a multi domain wildcard can secure different wildcard domains and their subdomains. The below example can clarify about multi domain wildcard SSL certificates where a different level of domains can secure their subdomains.

  • *.domain1.com
  • *.subdomain1.domain2.com
  • *.a1.subdomain2.domain3.com
  • *.a2.subdomain.mydomain.com

Code Signing Certificate:

Code Signing certificate authenticates the publisher’s identity and ensures code integrity. Code signing certificate follows two types of validations like organization validation and extended validation (EV Code Signing certificate). If we talk about the EV Code Signing certificate, then EV Code signing with the help of the Microsoft Smart Screen filter builds the reputation of the publisher. Generally, the developer uses a private key to sign a code and users apply a public key to verify the publisher’s identity. Few famous brands deal with Code Signing certificates.

Comodo Code Sign: Comodo Code Signing certificate is a branded certificate that authenticates the code and assures users that the code is from the original source. Moreover, a timestamp will never let your code invalid even the certificate itself expires. It helps to increase downloads of software and assures that the code is not modified since it is signed.

Comodo EV Code Sign: Comodo EV Code Signing certificate builds immediate publisher’s reputation with Microsoft SmartScreen filter technology. Distributors can distribute software code easily on third-party platforms also. Comodo thoroughly checks business existence with third-party sources too. Comodo EV Code Sign certificate removes pesky download warnings. A private key is kept on an external hardware token to avoid hacking activities.

DigiCert Code Signing Certificate: DigiCert Code Signing certificate can sign code for drivers, software, applications. The certificate confirms that the code is from the original source and not tampered with. Due to organization validation, DigiCert checks business presence with registered business documents and third-party databases. Users will not get an ‘Unknown Publisher’ warning while downloading the software. The code signing certificate supports multiple platforms (Java, Adobe AIR, Office, and VBA, MS Authenticode, Windows phone).

Client Certificate:

A client certificate is a data file that authenticates the client’s identity to the server. There is no data transmission involved in the client certificate. A client certificate is also named an email certificate in which the email sender signs the communication, and the receiver confirms the digital signature. In the browser, the Client Authentication ( is represented as client certificate OID (object identifier) under Extended Key Usage details. When a user requests to access a secured database, it has to pass through two-factor authentication in the client certificate.

Recommended: Server Certificate vs Client Certificate


Each certificate has its importance and is useful in different situations like the TLS certificate is for securing online transactions where Code signing certificate is to sign software code. However, the object of a digital certificate is to verify the identity and encrypt the information. A digital certificate is necessary to provide integrity, authenticity, Non-repudiation and all these elements are required in the security world.


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