1. Network and Internet Security Prepared by Dr. Lamiaa Elshenawy
Computer Security
Lecture 8
Ch.16
Network and Internet Security
Prepared by Dr. Lamiaa Elshenawy

2. Outline Transport-level security Web Security Considerations
Secure Socket Layer and Transport Layer Security
Transport Layer Security (TLS)
HTTPS
Secure Shell (SSH)

3. Transport-level security Key Points
Internet security : is a branch of computer security browser security
Secure Socket Layer (SSL) security services between TCP (Transmission Control Protocol) and applications use TCP Transport Layer Service (TLS)
SSL/TLS confidentiality & data integrity symmetric encryption & message authentication code (MAC)
HTTPS (HTTP over SSL) combination of HTTP and SSL secure communication between Web browser & web server
involves
provides by
provides by
Refers to
implement

4. Transport-level security Web Security Considerations
Internet is two-way Web is vulnerable to attacks
Business transactions Reputations damaged and money lost Web servers subverted
Web software hide many potential
security flaws vulnerable to a variety of security attacks

5. Transport-level security Web Security Considerations
Web server launching pad attacker access data systems connected to server at local site
Untrained (in security matters) users are common clients Web-based services not have tools or knowledge to effective countermeasures

6. Transport-level security Threats on Web

7. Transport-level security Secure Socket Layer and Transport Layer Security
SSL provides basic security services to various higher layer protocols (Hypertext Transfer Protocol (HTTP)), which provides the transfer service for Web client/server interaction
SSL architecture

8. Transport-level security Handshake Protocol
Most complex part of SSL
Used before any application data is transmitted
Allows the server and client to authenticate each other
Negotiate an encryption & MAC algorithm & cryptographic keys to protect data
Handshake Protocol

9. Transport-level security Handshake Protocol
Type (1 byte) Indicates one of 10 messages
Length (3 bytes) length of the message in bytes
Content (≥ 0 bytes) parameters associated with this message

10. Transport-level security Handshake Protocol

11. Transport-level security Change Cipher Spec Protocol
Least complex part of SSL
Consists of a single message (single byte with the value 1)
Updates cipher suite to be used on this connection
Change Cipher Spec Protocol

12. Transport-level security Alert Protocol
Convey SSL-related alerts to the peer entity
Alert messages are compressed and encrypted
Each message in this protocol consists of two bytes 1
Unexpected_ message
warning
fatal
An appropriate message was received 2

13. Transport-level security SSL Record Protocol
SSL Record Protocol provides two security services
Confidentiality: Handshake Protocol defines a shared secret key that is used for conventional encryption
Message Integrity: Handshake Protocol defines a shared secret key that is used to form a message authentication code (MAC)

14. Transport-level security SSL Record Protocol
SSL Record protocol Operation

15. Transport-level security SSL Record Protocol
Content Type (8 bits): Higher-layer protocol used to process the enclosed fragment.
Major Version (8 bits): Indicates major version of SSL in use (SSLv3--- value= 3)
Minor Version (8 bits): Indicates minor version of SSL in use (SSLv3--- value= 0)
Compressed Length (16 bits): The length of the plaintext fragment (Max= )

16. Transport-level security: HTTPS
What is HTTPS?
HTTPS built into all modern Web browsers
URL (uniform resource locator)
port 443
port 80

17. Transport-level security: SSH
What is SSH?
Secure Shell (SSH) is a protocol for secure network communications designed to be simple and inexpensive
What are versions of SSH?
SSH /file transfer
SSH fixes security flaws of SSH1

18. Transport-level security: SSH
SSH Protocol Stack

19. Thank you for your attention