SSL/TLS Handshakes Quiz

Deep Dive into SSL and TLS Handshakes

• The video features David Bombal and Ed discussing the SSL and TLS handshake.

• Ed runs a YouTube channel on network engineering and security training.

• The SSL/TLS handshake provides confidentiality, integrity, and authentication.

• Confidentiality is achieved through symmetric encryption while integrity is achieved through hashing and message authentication code (MAC).

• MAC combines the key and message to provide integrity and authentication.

• Key exchange is necessary for symmetric encryption and can be done through asymmetric encryption using algorithms like Diffie-Hellman or RSA.

• RSA is a common asymmetric encryption algorithm that creates a set of public and private keys.

• The SSL/TLS handshake involves exchanging messages between the client and server to establish a secure connection.

• The handshake includes a ClientHello message, ServerHello message, Certificate message, ServerKeyExchange message, ClientKeyExchange message, and ChangeCipherSpec message.

• The session keys derived from the handshake are used to secure the data in SSL communication.

• The SSL/TLS handshake happens every time a user accesses a website over HTTPS or uses an SSL VPN.

• Ed offers a full eight-hour course on SSL/TLS and cryptography on his YouTube channel.SSL/TLS Handshake and Asymmetric Encryption

• Symmetric encryption uses the same key for both encryption and decryption, while asymmetric encryption uses two different keys.

• Asymmetric encryption can only go forward, and the math involves trapdoor functions that can only go in one direction.

• RSA creates two mathematically linked keys, one public and one private, that can be used in either direction.

• Public and private keys can be used for confidentiality, authentication, and integrity.

• A message can be encrypted with the recipient's public key to ensure confidentiality, and only the recipient's private key can decrypt it.

• A message can be encrypted with the sender's private key to ensure authenticity, and anyone with the sender's public key can decrypt it to verify that it came from the sender.

• SSL/TLS has three goals: confidentiality, integrity, and authentication.

• Symmetric encryption and MAC are used for confidentiality and integrity, and RSA or Diffie-Hellman are used for key exchange and authentication.

• A cipher suite is an explicit definition of the protocols used for key exchange, authentication, encryption, and hashing.

• The SSL handshake involves exchanging information between the client and server to establish a secure connection.

• The server has a certificate proving its identity, which is signed by a certificate authority.

• The goal of the SSL handshake is to create session keys that will be used for encrypting and protecting the data on the wire.Overview of SSL/TLS Handshake Process

• The SSL/TLS handshake process begins with the server acquiring its certificate, public key, and private key before the client shows up.

• The first message in a TLS session is the Client Hello, which includes the version number, random number, session ID, and Cipher Suite list.

• The server responds with the Server Hello, which includes the same five fields as the Client Hello, indicating the highest mutually accepted version of SSL/TLS, a random number, session ID, and the selected Cipher Suite.

• Both the client and server have acquired new information, including the highest mutually supported version of SSL/TLS, random numbers, session ID, and the selected Cipher Suite.

• All of this information is sent in clear text, making it vulnerable to interception by a third party.

• The server sends the certificate message, which includes the certificate and public key of the server, and the client acquires these two new pieces of information.

• The server then sends the Server Hello Done message, indicating that this is all the server intends to send in this step of the handshake process.

• The certificate message includes the full certificate chain, which goes all the way back to the certificate issuer (e.g. Verisign, Let's Encrypt, DigiCert, Comodo).

• There are different versions of the handshake process, but the Server Hello Done message indicates that the server is not using any of those versions.

• The SSL/TLS handshake process includes a total of nine messages, but the first three (Client Hello, Server Hello, Certificate) are the most important.

• The Cipher Suite list in the Client Hello allows the server to choose a Cipher Suite that both parties support, ensuring secure communication.

• The SSL/TLS handshake process is essential for secure communication over the internet, as it establishes the parameters for encryption and authentication.SSL/TLS Handshake Process: Client Key Exchange and Session Key Generation

• The Client Key Exchange message is sent by the client in the SSL/TLS handshake process.

• The Client Key Exchange message serves two purposes: to establish keying material or a SEED value, and to prove that the server is the true owner of the certificate.

• The Pre Master Secret is a special value that is used to accomplish both of these goals in the Client Key Exchange message.

• The Pre Master Secret is 48 bytes long, and is randomly generated by the client.

• The Pre Master Secret is encrypted with the server's public key and sent over the wire.

• Only the server, which has the corresponding private key, can decrypt the Pre Master Secret and obtain the unencrypted value.

• Both parties use the Pre Master Secret to generate the Master Secret, which is used to create the session keys.

• The Master Secret is created by combining the Pre Master Secret with the literal string "Master Secret," the random numbers exchanged in the Client Hello and Server Hello messages, and a hashing algorithm.

• The Master Secret is turned into the session keys by combining it with the literal string "key expansion," the same random numbers used before, and a Pseudo Random Function (PRF).

• The PRF is used to generate as many bytes of key material as needed for the Cipher Suite being used.

• The PRF ensures that both parties end up with the same sequence of bytes for the session keys.

• SSL/TLS generates two secure tunnels, one for data sent from the client to the server, and one for data sent from the server to the client. The same set of keys is used for both directions of each tunnel.