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SSL Layer

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Trinh Phuc Tho
Trinh Phuc Tho

The Secure Socket Layer (SSL) protocol provides transport layer security to TCP applications like web browsers and servers for e-commerce. It offers security services like server authentication, data encryption, and optional client authentication. During the SSL handshake, the client authenticates the server via a certificate signed by a Certificate Authority. A master secret key is then generated and used to derive separate encryption and MAC keys to securely transmit data in both directions.

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The Secure Socket Layer (SSL Protocol)
8: Network Security 8-2 Secure sockets layer (SSL) • provides transport layer security to any TCP-based application using SSL services. – e.g., between Web browsers, servers for e-commerce (shttp) • security services: – server authentication, data encryption, client authentication (optional) TCP IP TCP enhanced with SSL TCP socket Application TCP IP TCP API SSL sublayer Application SSL socket
TCP Handshake & SSL Handshake 1. Handshake: • Bob establishes TCP connection to Alice • authenticates Alice via CA signed certificate • creates, encrypts (using Alice’s public key), sends master secret key to Alice decrypt using KA - to get MS create Master Secret (MS)
8-4 2. Key Derivation: • Alice, Bob use shared secret (MS) to generate 4 keys: – EB: Bob->Alice data encryption key – MB: Bob->Alice MAC key – EA: Alice->Bob data encryption key – MA: Alice->Bob MAC key Used for sending data from Bob to Alice Used for sending data from Alice to Bob Now, both Bob and Alice share the same 4 keys (Ea,Ma,Eb,Mb)
H( ). MB b1b2b3 … bn d d H(d) d H(d) H( ). EB byte stream: block n bytes together SSL seq. # d H(d)Type Ver Len SSL record encrypted using EBunencrypted b1b2b3 … bn d d H(d) d H(d) decrypt using EB & SSL seq.# d H(d)Type Ver Len encrypted using EBunencrypted TCP/IP Transmission Check for integrity MB 3. Data Transfer
8-6 4. Connection Closure • SSL 2.0 terminates the underlying TCP connection by simply sending TCP FIN segment => give chances for Truncation Attack • Solution: SSL 3.0 (TLS) introduces closing handshake, the recipient knows the message has not ended until this action has been performed.

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SSL Layer

  • 1. The Secure Socket Layer (SSL Protocol)
  • 2. 8: Network Security 8-2 Secure sockets layer (SSL) • provides transport layer security to any TCP-based application using SSL services. – e.g., between Web browsers, servers for e-commerce (shttp) • security services: – server authentication, data encryption, client authentication (optional) TCP IP TCP enhanced with SSL TCP socket Application TCP IP TCP API SSL sublayer Application SSL socket
  • 3. TCP Handshake & SSL Handshake 1. Handshake: • Bob establishes TCP connection to Alice • authenticates Alice via CA signed certificate • creates, encrypts (using Alice’s public key), sends master secret key to Alice decrypt using KA - to get MS create Master Secret (MS)
  • 4. 8-4 2. Key Derivation: • Alice, Bob use shared secret (MS) to generate 4 keys: – EB: Bob->Alice data encryption key – MB: Bob->Alice MAC key – EA: Alice->Bob data encryption key – MA: Alice->Bob MAC key Used for sending data from Bob to Alice Used for sending data from Alice to Bob Now, both Bob and Alice share the same 4 keys (Ea,Ma,Eb,Mb)
  • 5. H( ). MB b1b2b3 … bn d d H(d) d H(d) H( ). EB byte stream: block n bytes together SSL seq. # d H(d)Type Ver Len SSL record encrypted using EBunencrypted b1b2b3 … bn d d H(d) d H(d) decrypt using EB & SSL seq.# d H(d)Type Ver Len encrypted using EBunencrypted TCP/IP Transmission Check for integrity MB 3. Data Transfer
  • 6. 8-6 4. Connection Closure • SSL 2.0 terminates the underlying TCP connection by simply sending TCP FIN segment => give chances for Truncation Attack • Solution: SSL 3.0 (TLS) introduces closing handshake, the recipient knows the message has not ended until this action has been performed.