1. Web Security (TRANSPORT-LEVEL SECURITY)
Secure Socket Layer
Transport Layer Security

2. Web Security
◆ Secure Socket Layer (SSL) provides security services between TCP and applications that use TCP. The Internet standard version is called Transport Layer Service (TLS).
◆ SSL/TLS provides confidentiality using symmetric encryption and message integrity using a message authentication code.
◆ SSL/TLS includes protocol mechanisms to enable two TCP users to determine the security mechanisms and services they will use.

3. Web Security Threats

4. Web Traffic Security Approaches

5. 1. SECURE SOCKET LAYER
Two important SSL concepts are the SSL session and the SSL connection, which are defined in the specification as follows. • Connection: A connection is a transport (in the OSI layering model definition) that provides a suitable type of service. For SSL, such connections are peer-to-peer relationships. The connections are transient. Every connection is associated with one session. • Session: An SSL session is an association between a client and a server. Sessions are created by the Handshake Protocol. Sessions define a set of cryptographic security parameters which can be shared among multiple connections

6. session state
A session state is defined by the following parameters. • Session identifier • Peer certificate • Compression method • Cipher spec • Master secret • Is resumable

7. connection state
A connection state is defined by the following parameters.
Server and client random
Server write MAC secret
Client write MAC secret
Server write key
Client write key
Initialization vectors
Sequence numbers

8. SSL Architecture

9. SSL Record Protocol
The SSL Record Protocol provides two services for SSL connections: • Confidentiality: The Handshake Protocol defines a shared secret key that is used for conventional encryption of SSL payloads. • Message Integrity: The Handshake Protocol also defines a shared secret key that is used to form a message authentication code (MAC).

10. SSL Record Protocol Operation

11. SSL Record Protocol header
• Content Type (8 bits): The higher-layer protocol used to process the enclosed fragment. • Major Version (8 bits): Indicates major version of SSL in use. For SSLv3, the value is 3. • Minor Version (8 bits): Indicates minor version in use. For SSLv3, the value is 0. • Compressed Length (16 bits): The length in bytes of the plaintext fragment (or compressed fragment if compression is used)

12. SSL Record Format

13. SSL Record Protocol Payload

14. Alert Protocol Messages
• unexpected_message • bad_record_mac • decompression_failure • handshake_failure • illegal_parameter • close_notify • no_certificate • bad_certificate • unsupported_certificate • certificate_revoked • certificate_expired • certificate_unknown:

15. Handshake Protocol

16. 2. TRANSPORT LAYER SECURITY
Version Number
Message Authentication Code
Pseudorandom Function
Alert Codes
Cipher Suites
Client Certificate Types
Cryptographic Computations
Padding

17. Pseudorandom Function

18. Alert Codes record_overflow unknown_ca access_denied decode_error
protocol_version
insufficient_security
unsupported_extension
internal_error
decrypt_error