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SSL/TLS Handshake Protocol

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SSL/TLS Operation Layer

operation-layer

The SSL/TLS protocol operates on:

  • Application / Presentation / Session layers of OSI model
  • Application layer of TCP/IP model

SSL/TLS Handshake Process

handshake-all

Step 1 ClientHello

step1

Step 2 ServerHello

step2

Step 3 Verify Digital Certificate

step3
The client will contact the server’s CA(certificate authority) and verify the server’s digital certificate, thus confirming the authenticity of the web server.
GOAL: Establishing the trust on the web server.

Step 4 ClientKeyExchange

step4

Step 5 Finished(client)

step5

Step 6 Finished(server)

step6

Step 7 Handshake Done. Exchanged Message

step7
Once the handshake is done, the server and client can now exchange messages that are symmetrically encrypted with the shared secret key.

Notes

  1. The above process demonstrates how asymmetric key algorithm and symmetric key algorithm work together.
  • Asymmetric key algorithm (public key & private key) is used to verify the identity of the owner and its public key so that trust is built.
  • Once the connection is established, Symmetric key algorithm (shared key) is used to encrypt and decrypt all traffic between them.

  1. The green padlock: indicates that the web server’s public key really belongs to the web server, not someone else.

  2. The Https and the green padlock only indicates the communications between client and server are encrypted. It does not says the website is “safe and good”.

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