SSL/TLS Certificates

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🔐 SSL/TLS CERTIFICATES

📘 What is SSL/TLS?

SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are cryptographic protocols used to secure communication between a client (browser) and a server (website).

TLS is the modern, more secure version of SSL.

Today, we use TLS, but the term “SSL Certificate” is still commonly used.

📘 What is an SSL/TLS Certificate?

An SSL/TLS Certificate is a digital certificate that:

  • Authenticates the identity of a website

  • Encrypts data exchanged between browser and server

  • Prevents data interception by attackers

When a website uses SSL/TLS, its URL starts with:

👉 https://
And shows a 🔒 lock icon in the browser.

🎯 Purpose of SSL/TLS Certificate

  1. Encrypt communication

  2. Protect sensitive data

  3. Verify website identity

  4. Prevent man-in-the-middle attacks

🔑 How SSL/TLS Works (Step-by-Step)

This process is called the TLS Handshake.

Step 1: Client Hello

Browser sends request to server asking for secure connection.

Step 2: Server Hello

Server sends:

  • SSL/TLS certificate

  • Public key

Step 3: Certificate Verification

Browser verifies:

  • Certificate validity

  • Issuing Certificate Authority

  • Expiry date

Step 4: Session Key Creation

Browser creates a symmetric session key.
Encrypts it using server’s public key.

Step 5: Secure Communication Begins

Server decrypts session key using private key.
Now both use symmetric encryption for fast communication.

🔥 Types of SSL/TLS Certificates

1️⃣ Domain Validation (DV)

  • Basic level certificate

  • Only verifies domain ownership

  • Issued quickly

  • Suitable for small websites

2️⃣ Organization Validation (OV)

  • Verifies business identity

  • Higher trust level

  • Suitable for company websites

3️⃣ Extended Validation (EV)

  • Highest level of validation

  • Shows company name in address bar

  • Used by banks and large companies

🔑 Based on Domain Coverage

Single Domain Certificate

Secures one domain.

Wildcard Certificate

Secures main domain + all subdomains.

Example:
*.example.com

Multi-Domain Certificate (SAN)

Secures multiple different domains.

📜 What Information is in SSL Certificate?

  • Domain name

  • Organization name

  • Public key

  • Issuer (Certificate Authority)

  • Expiration date

  • Digital signature

🏢 Who Issues SSL Certificates?

Trusted Certificate Authorities (CA) issue SSL certificates.

Examples:

  • DigiCert

  • GlobalSign

  • Let's Encrypt

  • Sectigo

🛡 Benefits of SSL/TLS

  • Data encryption

  • Secure online payments

  • Prevents data theft

  • Improves SEO ranking

  • Builds customer trust

⚠ What Happens Without SSL?

  • Browser shows “Not Secure” warning

  • Data can be intercepted

  • Risk of hacking

  • Loss of trust

🔥 SSL vs TLS

FeatureSSLTLS
VersionOlderNewer
SecurityLess secureMore secure
Used TodayNoYes
SpeedSlowerFaster

🔐 Encryption Used in SSL/TLS

SSL/TLS uses:

  1. Asymmetric encryption → for key exchange

  2. Symmetric encryption → for data transfer

  3. Hashing → for integrity

🚨 Common SSL Attacks

  • Man-in-the-Middle Attack

  • SSL Stripping

  • Fake Certificates

  • Expired Certificates misuse

🎓 Exam Short Note

SSL/TLS certificates are digital certificates issued by trusted Certificate Authorities that authenticate websites and encrypt communication between users and servers to ensure confidentiality, integrity, and secure online transactions.

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