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EMTM 553: E-commerce Systems

Lecture 7: Implementing Security

Insup Lee

Department of Computer and Information Science

University of Pennsylvanialee@cis.upenn.edu

www.cis.upenn.edu/~lee

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Protecting ElectronicCommerce Assets

• You cannot hope to produce secure commerce systems unless there is a written security policy– What assets are to be protected– What is needed to protect those assets– Analysis of the likelihood of threats– Rules to be enforced to protect those assets

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Protecting ElectronicCommerce Assets

• Both defense and commercial security guidelines state that you must protect assets from– Unauthorized disclosure– Modification– Destruction

• Typical security policy concerning confidential company information– Do not reveal company confidential information to

anyone outside the company

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Minimum Requirements for Secure Electronic Commerce

Figure 6-1

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Protecting Intellectual Property

• The dilemma for digital property is how to display and make available intellectual property on the Web while protecting those copyrighted works

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Companies Providing Intellectual Property Protection Software

• ARIS Technologies (part of verance.com)– Digital audio watermarking systems

o Embedded code in audio file uniquely identifying the intellectual property

• Digimarc Corporation– Watermarking for various file formats– Controls software and playback devices

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Companies Providing Intellectual Property Protection Software

• SoftLock Services– Allows authors and publishers to lock files containing

digital information for sale on the Web– Posts files to the Web that must be unlocked with a

purchased ‘key’ before viewing

• Digitalgoods.com– infrastructure and integrated services necessary to

securely market and distribute multimedia digital content to its maximum audience

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Protecting Client Computers

• Active content, delivered over the Internet in dynamic Web pages, can be one of the most serious threats to client computers

• Threats can hide in– Web pages– Downloaded graphics and plug-ins– E-mail attachments

• Misplaced trust– Web sites that aren’t really what they seem and trick

the user into revealing sensitive data

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Protecting Client Privacy

• Cookies– Small pieces of text stored on your computer and

contain sensitive information that is not encrypted– Anyone can read and interpret cookie data– Do not harm client machines directly, but potentially

could still cause damage– Two types: session cookie and persistent cookie

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Dealing with Cookies

• Can be set to expire within 10, 20, or 30 days• Retrievable only by the site that created them• Collect information so that the user doesn’t

have to continually enter usernames and passwords to access Web sites

• Earlier browsers simply stored cookies without comment

• Today’s browsers allow the user to– Store cookies without permission or warning– Receive a warning that a cookie is about to be stored– Unconditionally disallow cookies altogether

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Monitoring Active Content

• Netscape Navigator and Microsoft Internet Explorer browsers are equipped to allow the user to monitor active content before allowing it to download

• Digital certificates provide assurance to clients and servers that the participant is authenticated

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Digital Certificates

• Also known as a digital ID• An attachment to an e-mail message• Embedded in a Web page• Serves as proof that the holder is the person or

company identified by the certificate• Encoded so that others cannot read or

duplicate it• Ex: visit www.amazon.com and click on a

padlock

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VeriSign

• Oldest and best-known Certification Authority (CA)

• Offers several classes of certificates– Class 1 (lowest level)

o Bind e-mail address and associated public keys– Class 4 (highest level)

o Apply to servers and their organizationso Offers assurance of an individual’s identity and

relationship to a specified organization

• Visit www.verisign.com

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Structure of a VeriSign CertificateFigure 6-4

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Microsoft Internet Explorer

• Provides client-side protection right inside the browser

• Reacts to ActiveX and Java-based content• Authenticode verifies the identity of

downloaded content• The user decides to ‘trust’ code from individual

companies

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Security Warning and Certificate ValidationFigure 6-5

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Internet Explorer Zones and Security LevelsFigure 6-6

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Internet Explorer Security Zone Default SettingsFigure 6-7

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Netscape Navigator

• User can decide to allow Navigator to download active content

• User can view the signature attached to Java and JavaSript

• Security is set in the Preferences dialog box• Cookie options are also set in the Preferences

dialog box

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Setting Netscape Navigator PreferencesFigure 6-8

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A Typical Netscape Navigator Java Security Alert

Figure 6-9

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Viewing a Content Provider’s CertificateFigure 6-10

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Protecting Electronic Commerce Channels

• Protecting assets while they are in transit between client computers and remote servers

• Providing channel security includes– Channel secrecy– Guaranteeing message integrity– Ensuring channel availability– Authentication

• Cannot prevent eavesdropping through snooping in general

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Providing Transaction Privacy

• Encryption– The coding of information by using a mathematically

based program and secret key to produce unintelligible characters

– Steganographyo Makes text invisible to the naked eye

– Cryptographyo Converts text to strings that appear to have no

meaning

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Encryption

• 40-bit keys are considered minimal,128-bit keys provide much more secure encryption

• Encryption can be subdivided into three functions– Hash Coding

o Calculates a number from any length string– Asymmetric (Public-key) Encryption

o Encodes by using two mathematically related keys– Symmetric (Private-key) Encryption

o Encodes by using one key, both sender and receiver must know

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Hash Coding, Private-key, and Public-key EncryptionFigure 6-11

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Significant Encryption Algorithms and StandardsFigure 6-12

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Secure Sockets

Layer (SSL) Protocol

• Developed by Netscape Communications• Secures connections between two computers• Provides a security handshake in which the

client and server computers exchange the level of security to be used, certificates, among other things

• Secures many different types of communications between computers

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Secure Sockets

Layer (SSL) Protocol

• Provides either 40-bit or 128-bit encryption• Session keys are used to create the cipher text

from plain text during the session• The longer the key, the more resistant to

attack• Protocol is called https

– Ex: www.amazon.com

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SSL Handshake

The SSL handshake consists of nine steps that authenticate the two parties and create a shared session key. [Stein]

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SSL Web Server InformationFigure 6-14

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Secure HTTP (S-HTTP) Protocol

• Developed by CommerceNet Consortium• Extension to HTTP that provides numerous security

features– Client and server authentication– Spontaneous encryption– Request/response nonrepudiation

• Provides symmetric and public-key encryption, and message digests (summaries of messages as integers)

• Whereas SSL is designed to establish a secure connection between two computers, S-HTTP is designed to send individual messages securely.

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Ensuring Transaction IntegrityFigure 6-15

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Guaranteeing Transaction Delivery

• Neither encryption nor digital signatures protect packets from theft or slowdown

• Transmission Control Protocol (TCP) is responsible for end-to-end control of packets

• TCP requests that the client computer resend data when packets appear to be missing

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Protecting theCommerce Server

• Access control and authentication– Controlling who and what has access to the server– Requests that the client send a certificate as part of

authentication– Server checks the timestamp on the certificate to

ensure that it hasn’t expired– Can use a callback system in which the client

computer address and name are checked against a list

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Protecting theCommerce Server

• Usernames and passwords are the most common method of providing protection for the server

• Usernames are stored in clear text, while passwords are encrypted

• The password entered by the user is encrypted and compared to the one on file

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Logging On With A Username And PasswordFigure 6-16

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Operating System Controls

• Most operating systems employ username and password authentication

• A common defense is a firewall– All traffic from inside to outside and outside to inside

must pass through it– Only authorized traffic is allowed– The firewall itself must be immune to penetration

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ApplicationApplication

Firewalls

smtp: 25

ftp: 21

telnet: 23

http: 80

ftp: 21

PresentationPresentation

SessionSession

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

OSI

Site 2

Site 1Internet

Traffic Cop

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Check Point Software’s Firewall-1 Web PageFigure 6-17