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SSL/TLS Handshake Simulator

Visualize how SSL/TLS handshakes work with certificate verification, key exchange, and cipher negotiation. Compare TLS 1.2 and 1.3 protocols.

Category: Security

Topics covered: security, networking, tls, ssl, certificates, educational

// simulator

SSL/TLS Handshake Simulator

Visualize how SSL/TLS handshakes work with certificate verification, key exchange, and cipher negotiation. Compare TLS 1.2 and 1.3 protocols.

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How to use this simulator

Watch how your browser establishes a secure HTTPS connection. Use the Play button for auto-advance, or Next/Prev to step through manually. Each step shows what data is exchanged between client and server.

💡 Tip: Try different TLS versions and failure scenarios to see how the handshake changes.

SSL/TLS Handshake

Visualize how secure connections are established

TLS Version
Scenario
Client
Server
1/5

ClientHello

Client initiates with key share

Client → Server
•TLS version: 1.3
•Random bytes (32 bytes)
•Cipher suites (AEAD only)
•Key share extension (ECDHE)
•Supported versions extension
TLS 1.2 vs TLS 1.3

TLS 1.2

  • • 2 round-trips (2-RTT) to establish
  • • Supports older cipher suites
  • • RSA key exchange still allowed
  • • Separate ChangeCipherSpec message
  • • Widely supported (legacy systems)

TLS 1.3
Recommended

  • • 1 round-trip (1-RTT) - 50% faster!
  • • Only AEAD ciphers (more secure)
  • • Perfect Forward Secrecy required
  • • Encrypted earlier in handshake
  • • 0-RTT resumption possible

Key Concepts

Cipher Suite

A combination of algorithms: key exchange (ECDHE), authentication (RSA/ECDSA), encryption (AES-GCM), and hashing (SHA256).

Perfect Forward Secrecy

Even if the server's private key is compromised, past sessions remain secure because each session uses unique ephemeral keys.

Certificate Authority (CA)

A trusted organization that issues digital certificates. Browsers have a list of trusted root CAs built-in.

AEAD (Authenticated Encryption)

Combines encryption and authentication in one step (e.g., AES-GCM). Required in TLS 1.3 for better security.

Understanding SSL/TLS Handshakes

What you'll learn

  • How TLS 1.2 and TLS 1.3 handshakes differ
  • Certificate chain validation process
  • Key exchange mechanisms (RSA, ECDHE)
  • Cipher suite negotiation
  • Common TLS failure scenarios
  • Perfect Forward Secrecy (PFS)

TLS versions

  • TLS 1.3: Latest version with 1-RTT handshake, mandatory PFS, and removed insecure algorithms.
  • TLS 1.2: Still widely used, 2-RTT handshake with optional PFS.
  • TLS 1.0/1.1: Deprecated, should not be used due to security vulnerabilities.

Key concepts

  • Certificate: Digital document that binds a public key to an identity.
  • Cipher Suite: Set of algorithms for encryption, authentication, and key exchange.
  • PFS:Ensures session keys aren't compromised even if server's private key is.
  • AEAD: Authenticated Encryption with Associated Data (e.g., AES-GCM).

Best practices

  • Use TLS 1.3 where possible, TLS 1.2 as minimum.
  • Disable weak cipher suites (RC4, DES, export ciphers).
  • Enable HSTS to prevent protocol downgrade attacks.
  • Keep certificates up to date and use short validity periods.
  • Use Certificate Transparency (CT) logging.

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