Presented By: Atish Baul Module: CSYM020, Internet Security Course: MSc Internet Computing

Contents 1.Introduction 2.SSL Architecture 3.Analysis of an SSL Session 4.Applications of SSL 5.Implementation of SSL 6.Winning Features 7.References 2

1. Introduction What are SSL and TLS 3  Secure Socket Layer (SSL) and it's successor Transport Layer Security (TLS) are cryptographic protocols meant for secure data transmission across the internet.  Prevent eavesdropping, tampering and message forgery within the transport framework.  Provides endpoint authentication and communications privacy.  Used for web browsing, , instant messaging, etc. Multitude of uses, as we shall see later.  Used for both – Client-to-server communication – Server to server communication

1. Introduction  Typically, only the server is authenticated, client remains un-authenticated.  Sometimes both parties are authenticated. This is called "Mutual Authentication“. Manner of Usage 4

1. Introduction  Developed by Netscape as SSL 1.0 in 1996 for use with HTTP only, to secure communications between browser and client.  SSL has been endorsed by leading financial institutions (e.g. Visa, Master Card, etc) for commerce over the internet.  Still being updated and maintained by Netscape as SSL 2.0 and SSL 3.0, with endorsement from IETF and leading commercial bodies.  SSL 3.0 was used as basis for TLS 1.0 in 1999, an IETF standard protocol.  Specifications for TLS 1.1 were released in April It is a minor upgrade to TLS 1.0  SSL continues to be used alongside TLS, due to widespread support and legacy implementation. History of SSL, TLS 5

1. Introduction  SSL and TLS - Twin brothers.  Both protocols are so similar we can refer to them as one name, e.g.. SSL/TLS only.  They are similar, but they are not interchangeable.  Important difference is that TLS 1.0 applies a Keyed-Hashing for Message Authentication Code (HMAC) algorithm, whereas SSL 3.0 applies the Message Authentication Code (MAC) algorithm for authenticating messages. Pair of Twins 6

1. Introduction  SSL 1.0 has been deprecated.  SSL 2.0 (Mainly Legacy support).  SSL 3.0 (Current, being replaced by TLS for new projects).  TLS 1.0 (Current).  TLS 1.1 (Newly Introduced, not widely supported). Prevalent Versions 7

2. Architecture 2. SSL ARCHITECHTURE 8

2. Architecture SSL/TLS Protocol Stack 9 ISO Open Systems Interconnect model SSL runs beneath application layers. E.g. HTTP, FTP, SMTP etc SSL runs above transport protocols such as TCP.

2. Architecture SSL/TLS can be used with any application based over TCP. It’s applications are endless! 10

3. Analysis of SSL/TLS Session 3. Analysis of an SSL/TLS Session 11

3. Analysis of SSL/TLS Session 1.Peer negotiation for algorithm support  The two communicating parties negotiate a suitable cryptographic algorithm which they both support.  The most secure algorithm supported by both parties is chosen. 2.Public Key Encryption based key exchange, and Certificate based authentication.  E.g. RSA, Diffie-Hellman, DSA, etc. 3.Symmetric cipher-based traffic encryption.  E.g. RC2, RC4, DES, 3DES, etc. Three Basic Phases 12

3. Analysis of SSL/TLS Session Lifecycle of an SSL/TLS Session (Server only Authentication) 13

3. Analysis of SSL/TLS Session  An SSL session is basically an exchange of records of different types.  Each record may be compressed, encrypted and signed with a Message Authentication Code (MAC).  Each record has a content_type field that specifies which protocol is being used.  Some SSL protocols and their Content_type 20 : ChangeCipherSpec 21 : Alert 22 : Handshake Protocol. 22 : Record Layer Protocol. 23 : Application protocol. Simplistic Description 14

4. Applications of SSL/TLS Applications of SSL/TLS 15

4. Applications of SSL/TLS  Securing HTTP connections, also referred to as HTTPS.  Identified by prefix to the URL (within the address bar).  Is also indicated by padlock symbol at the status bar of a browser.  Implemented by installing an SSL certificate at the server. Secure connection over - HTTPS 16

4. Applications of SSL/TLS  SSL is not just for the web, it is a suite of cryptographic protocols meant to be used in various ways.  Thus, HTTPS is different from just SSL.  Other ways SSL is commonly implemented in Client-Server mode: – File Transfer Protocol Secure (FTPS) – SSL over Database connections to SQL Server, Oracle, etc. – Secure .  Peer-to-peer or Server-to-Server (mutual authentication ) uses: – Secure Web services – Semantic Web – Virtual Private Network – Session Initiation Protocol (SIP) applications such as Internet Telephony using VoIP. 17 Secure connection over - HTTPS

4. Applications of SSL/TLS  Default Outlook express port configuration:  Outlook express configured to use SSL (With Gmail POP3/SMTP settings): Example – SSL over POP3/SMTP 18

4. Applications of SSL/TLS SSL also has a place within the proposed Semantic Web. 19 The trust architecture is based around SSL/TLS.

5. Implementation Implementation of SSL 20

5. Implementation  On the server, a Certificate Signing Request (CSR) is generated. This creates two cryptographic keys: – Public Key : used to encrypt message to the server. This is sent to the Certificate Authority (CA) and gets downloaded by browser clients. It is then used to encrypt message to server. – Private Key : Stored on server, used to decrypt secure messages encrypted using the public key.  This CSR is then submitted to a relevant CA, along with relevant legal organisational details – E.g. Thawte, Verisign, GoDaddy.  CA verifies that details provided by organisation are correct, and issues a certificate file.  This file is copied and installed on the server, and it is ready to accept secure connections. SSL certificate on Server 21

5. Implementation  SSL mechanisms need to be enabled within the web server. – E.g. Apache, Internet Information Server.  Apache web server has ‘modules’ that implement SSL: – OpenSSL – ModSSL – Apache-SSL Enabling SSL within Web Server 22

5. Implementation  A typical browser come pre-installed with a list of Certificate Authorities SSL on client (Browser) 23 Mozilla Firefox

5. Implementation  Browsers support a variety of SSL/TLS versions: Support for SSL/TLS versions 24 Mozilla Firefox

5. Implementation  Browser can download and display (when asked) complete certificate details of the server: Certificate Details 25 Mozilla Firefox displaying Gmail’s SSL Certificate

5. Implementation  The browser will connect to relevant CA and verify a number of details, and perform separate checks. It will usually issue warnings explaining the severity of discrepancies, if any: Security Checks by Client 26 Mozilla Firefox detects inconsistencies with Gmail.com’s SSL certificate.

6. Winning Features Winning Features of SSL/TLS 27

6. Winning Features  Integrity – No one tampers with the contents during transport. E.g. Man-in-the-middle attacks.  Privacy – Prevent eavesdropping by encrypting messages.  Authentication – Verify remote party’s identity. – YOU ARE who you say YOU ARE.  Non-repudiation – Digital signature prove that a message was actually sent by a party. Prime Features 28

6. Winning Features  Asymmetric Public-Private key structure alleviates need for special setup for each session.  Depends on Public Key Infrastructure (PKI) implemented via Certificate Authorities (CA).  Conventions followed by manufacturers to pre-set software and appliances with globally agreed data. No setup per session or machine! 29

6. Winning Features  Uses X.509 certificate  OpenPGP certificates have been proposed for inclusion. Certificates 30

6. Winning Features  Previously limited to 40-bit symmetric keys by US govt restrictions  Now, 56-bit, 128-bit, 256-bit keys are commercially available, very easily.  2048-bit and 4096-bit keys are also supported by some products.  SSL/TLS itself does not restrict key size, but products and technologies on place have their own restrictions. Large key sizes 31

6. Winning Features  Cryptographic Algorithms can be rendered obsolete.  Extensible and upgradeable structure ensures latest and strongest cryptographic algorithms are used always.  Current supports includes – RSA, Diffie-Hellman, DSA (for Public Key cryptography). – RC2, RC4, IDEA, DES, 3DES (for Symmetric Ciphers). – MD2, MD4, MD5, SHA (One Way hash functions).  …. And more will come. Future-Proofing 32

References Thawte (2006). Securing your Online Data Transfer with SSL - A guide to understanding SSL Certificates [online]. Available from: [Accessed 2 April 2007] IETF (2006). RFC 4346 The Transport Layer Security (TLS) Protocol Version 1.1. Bussler, C. et al (2002) A conceptual architecture for Semantic Web Enabled Services. Special section on semantic web and data management. [Pages 24 – 29]. Thawte (2006). Enrolment guide for thawte SSL Web Server Certificates and SGC Supercerts [online]. Available from: [April 2, 2007] Wikipedia (2007a). Transport Layer Security [online]. Available from: [April 02, 2007] Wikipedia (2007b). Semantic Web [online]. Available from: [Jan 2, 2007] Minai, A. (2007) Internet Security, Msc Internet Computing, CSYM020. University of Northampton,

Thank you! 34