ClientHello
Offers protocol versions, cipher suites, key share, SNI and ALPN.
SECURE APPLICATION TRANSPORT · TLS 1.3
Build trust before sending HTTP.
HTTPS is HTTP semantics carried inside a TLS-protected channel. Step through negotiation, certificate validation and key agreement, then inject realistic failures without dismissing a browser security warning.
HANDSHAKE SIMULATOR
From ClientHello to encrypted application data
A conceptual TLS 1.3 trace. Cryptographic details are simplified, but message order and trust decisions remain explicit.
Browsertrust store + policy
ClientNegotiationversion · cipher · ALPN
ClientHello ↔ ServerHelloCertificateidentity + chain
Leaf → Intermediate → RootEncrypted HTTPapplication data
GET / HTTP/…READY · Choose a certificate scenario.
IDLENo secure channel yet.
Round trips before HTTP0
Negotiated ALPN—
Trust decision—
CERTIFICATE INSPECTOR
A signed binding between a name and a public key
- Subject
- CN=warin.me
- Subject Alternative Names
- DNS:warin.me, DNS:www.warin.me
- Issuer
- Teaching Intermediate CA 01
- Validity
- 2026-07-01 00:00 UTC → 2026-09-29 23:59 UTC
- Public key
- ECDSA P-256
- Signature
- ecdsa-with-SHA256
- Key usage
- Digital Signature
- Extended key usage
- TLS Web Server Authentication
Encryption alone does not prove identity. The browser verifies time, host name, signatures, constraints and a chain ending at a locally trusted root.
WHAT EACH STEP ESTABLISHES
Negotiation, identity and fresh session keys
ServerHello
Selects compatible parameters and contributes a key share.
CertificateVerify
Proves possession of the private key associated with the certificate.
Finished
Authenticates the handshake transcript before application data begins.
BOUNDARIES
What TLS protects—and what remains observable
| Property | Protected | Important limitation |
|---|---|---|
| Confidentiality | HTTP path, headers and body inside TLS | Endpoints still see plaintext. |
| Integrity | Tampering is detected by authenticated encryption. | Does not make application data truthful. |
| Server identity | Certificate chain and name validation. | Depends on trust-store and CA governance. |
| Metadata | Some handshake fields are increasingly encrypted. | IP addresses, timing and traffic sizes remain observable. |
CLASSROOM TASKS
Diagnose without clicking through warnings
- Distinguish an expired certificate from a name mismatch.
- Explain why a self-signed certificate can encrypt but is not automatically trusted.
- Trace how SNI and ALPN solve different negotiation problems.
- Compare a full handshake with session resumption.
- Locate where a reverse proxy terminates TLS and where plaintext exists.
- Explain why HTTPS does not guarantee that a website is honest.