Domain Validation (DV) Certificates

• Overview: The DV certificate is the basic level of encryption and is the fastest issued. It validates the ownership of a domain but does not require any heavy checks of an organization.
• Use Case: For use in small websites or blogs where trust and authentication are not a big concern.
• Advantages: Issuance can be fast, mostly in minutes, and inexpensive.
• Disadvantages: Offers the least amount of trust since it only validates the ownership of the domain.

Organization Validation (OV) Certificates

• Overview: OV certificates provide medium levels of assurance whereby the organization's identification, existence, and domain ownership are checked.
• Use Case: Good for corporations and organizations ready to gain user confidence in their actual existence.
• Benefits: Organization details will appear in the certificate, providing more trust than DV.
• Disadvantages: It takes time for issuance because of the extra verification involved.

Extended Validation (EV) Certificates

• Overview: EV is the most secure form and instills much confidence as it involves thorough verification of an organization.
• Typical use: Best suited for e-commerce websites and banks in which users need to trust a website.
• Pros: A green address bar or other trust indicators on the browsers denote maximum security.
• Cons: More expensive and time-consuming in issuance due to much detailed verification processes.

Wildcard Certificates

• Overview: A wildcard SSL Certificate secures one domain and all subdomains at one level, such as *.example.com. It is, therefore, the best solution for an organization with multiple subdomains sharing the same domain. It is cost-effective; one certificate secures unlimited subdomains.
• Disadvantages: All subdomains are at risk if the wildcard certificate is compromised.

Multi-Domain (SAN) Certificates

• Overview: These are the types of certificates that allow multiple domains and subdomains to be enabled with one certificate.
• Use Case: Ideal for corporations with multiple websites operating under different domain names.
• Advantages: Offers ease of management and cost-effectiveness as it combines many certificates into one.
• Cons: It can only protect a few domains based on the certificate vendor.

Unified Communications Certificates (UCC)

• Description: These are for Office Communications environments; these certificates are configured to support various domains, including services.
• Use Case: Ideal for organizations that rely on Microsoft Exchange Server or Office Communications Server.
• Advantages: Secure various services and domains effectively within a unified communication configuration.
• Discussion: They may not function well in non-Microsoft environments.

Single-Name SSL Certificates

• Overview: This kind of SSL provides security for a single domain or a subdomain with focused protection provided.
• Use Case: Applicable in small websites or services that do not need coverage of several domains.
• Advantages: It is simple, straightforward, and usually cheaper when operating only a single domain.
• Disadvantages: Only one domain or subdomain per certificate; additional domains require separate certificates.

Code Signing Certificates

• Overview: Unlike the usual SSL certificates, code signing certificates are utilized for signing software and code digitally to be checked for authenticity and integrity.
• Use Case: Software developers must use it to assure users that their software is authentic and has not been tampered with.
• Pros: It creates trust among users because it verifies the integrity and source of the software.
• Cons: Like other SSL certificates, it does not encrypt data between a server and a client.

The right type of SSL certificate will be chosen according to your specific needs regarding validation level, domain number, and the kind of website or application. Where your requirements are basic encryption or fast certificate issuance, Domain Validation can serve the purpose. Extended Validation SSL is more desirable, specifically for high trust and security purposes within the confines of e-commerce or finance. A wildcard and multi-domain SSL offers flexibility and cost savings to organizations with multiple subdomains or domains.

Understanding the differences between these types can help individuals and organizations make informed decisions, ensuring that they provide their users with the appropriate security and trust. Investing in the correct SSL certificate is crucial for safeguarding sensitive information and enhancing the credibility of your online presence.

The SSL Handshake Process

SSL Handshake is a significant process in any establishment of a secure connection. It includes a step-by-step process that establishes an encrypted channel for communication. A step-by-step breakdown includes:

• Client Hello
  

  The client (browser) sends the server a "Client Hello" message. This message includes the client’s SSL version, cipher settings, session-specific data, and other information the server needs to communicate with the client.

• Server Hello
  

  The server responds with a "Server Hello" message. This message includes the server’s SSL version, chosen cipher, session ID, and digital certificate. The certificate contains the server’s public key and is signed by a trusted Certificate Authority (CA).

• Server Certificate and Key Exchange
  

  The server sends its digital certificate to the client, who verifies it against a list of trusted CAs. If the certificate is valid, the server may send a "Server Key Exchange" message if a different cipher is chosen.

• Client Key Exchange
  

  The client creates a "pre-master secret" and encrypts it with the server’s public key. This encrypted pre-master secret is sent to the server; only the server can decrypt it using its private key.

• Generating Session Keys
  

  The client and server use the pre-master secret to generate session keys, which are symmetric keys used to encrypt and decrypt information during the session. This ensures that even if someone intercepts the data, they cannot read it without the session keys.

• Client Finished
  

  The client sends a "Finished" message, encrypted with a session key, indicating that the client’s part of the handshake is complete.

• Server Finished
  

  The client sends a "Finished" message, encrypted with a session key, indicating that the client’s part of the handshake is complete.

Encryption and Data Integrity

SSL uses two types of encryption: asymmetric and symmetric.

• Asymmetric Encryption:Used during the handshake process to exchange the pre-master secret. It involves a pair of keys – a public key, which is shared, and a private key, which is kept secret.
• Symmetric Encryption:Used for data transmission after the handshake. It is faster and involves a single key for encryption and decryption, which is why it’s used for most data exchanges.

Data integrity is maintained using message authentication codes (MACs). These ensure that data is not altered during transmission.

Authentication and Trust

Authentication is a critical component of SSL, ensuring that the parties involved in communication are who they claim to be. This is achieved through digital certificates from trusted Certificate Authorities (CAs).

• Digital Certificates:These electronic documents use a digital signature to bind a public key with an identity. They include the certificate holder’s name, the certificate’s serial number, expiration dates, a copy of the certificate holder’s public key, and the digital signature of the CA.
• Certificate Authorities (CAs):Trusted entities that issue digital certificates. They verify the identity of organizations and individuals before issuing certificates.