HTTPS and Certificates

When you see the padlock and https://, your browser is using TLS (Transport Layer Security). TLS gives three things at once:

• Encryption: eavesdroppers on the Wi-Fi or network cannot read the traffic.
• Integrity: traffic cannot be altered unnoticed.
• Authentication: a certificate, signed by a trusted certificate authority, proves the site really belongs to the domain.

In brief: the browser and server use public-key cryptography to agree a shared secret key, then switch to fast symmetric encryption for the conversation. HTTPS does not mean a site is trustworthy: criminals get certificates for fake domains too. It means the connection to that domain is private.