Presented By:

Atish BaulModule: CSYM020, Internet SecurityCourse: MSc Internet Computing

Contents

1. Introduction2. SSL Architecture3. Analysis of an SSL Session4. Applications of SSL5. Implementation of SSL6. Winning Features7. References

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1. Introduction

What are SSL and TLS

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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, email, 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

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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 2006. 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

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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

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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

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2. Architecture

2. SSL ARCHITECHTURE

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2. Architecture

SSL/TLS Protocol Stack

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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!

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3. Analysis of SSL/TLS Session

3. Analysis of an SSL/TLS Session

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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

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3. Analysis of SSL/TLS Session

Lifecycle of an SSL/TLS Session(Server only Authentication)

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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

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4. Applications of SSL/TLS

Applications of SSL/TLS

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4. Applications of SSL/TLS

Securing HTTP connections , also referred to as HTTPS.

Identified by HTTPS:// 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

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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 email.

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.

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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

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4. Applications of SSL/TLS

SSL also has a place within the proposed Semantic Web.

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The trust architecture is based around

SSL/TLS.

5. Implementation

Implementation of SSL

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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

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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

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5. Implementation

A typical browser come pre-installed with a list of Certificate Authorities

SSL on client (Browser)

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Mozilla Firefox

5. Implementation

Browsers support a variety of SSL/TLS versions:

Support for SSL/TLS versions

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Mozilla Firefox

5. Implementation

Browser can download and display (when asked) complete certificate details of the server:

Certificate Details

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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

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Mozilla Firefox detects

inconsistencies with

Gmail.com’s SSL certificate.

6. Winning Features

Winning Features of SSL/TLS

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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

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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!

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6. Winning Features

Uses X.509 certificate

OpenPGP certificates have been proposed for inclusion.

Certificates

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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

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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

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References

• Thawte (2006). Securing your Online Data Transfer with SSL - A guide to understanding SSL Certificates [online].Available from: http://www.thawte.com/ssl-digital-certificates/free-guides-whitepapers/ [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: http://www.thawte.com/ssl-digital-certificates/free-guides-whitepapers/ [April 2, 2007]

• Wikipedia (2007a). Transport Layer Security [online]. Available from: http://en.wikipedia.org/wiki/Transport_Layer_Security [April 02, 2007]

• Wikipedia (2007b). Semantic Web [online].Available from: http://en.wikipedia.org/wiki/Semantic_web [Jan 2, 2007]

• Minai, A. (2007) Internet Security, Msc Internet Computing, CSYM020. University of Northampton, 2007.

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Thank you!

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