Security Matters

V.T. Raja, Ph.D.,

Oregon State University

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Security Matters

• Outline

– Summary

– Example to illustrate RSA Algorithm– A framework to help managers

understand their role in security

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Summary from first lecture on Security

• Characteristics of Secure Communication

• Perfect security – a myth or a reality? • Ciphers and Cryptography

• Authentication (ap 1.0 - ap 5.0)

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Characteristics of Secure Communication

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Cryptography

• Ciphers– Caesar, Monoalphabetic, Polyalphabetic

• Symmetric Key Cryptography (SKC)– Basic idea of SKC– Notation for symmetric key– Some popular SKC algorithms– Sharing of symmetric key

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Public Key Cryptography (PKC)

• Basic idea of PKC

• Notation for private/public key pair and plain text message

• RSA Algorithm

• Sharing public key– Sender/Receive Authentication– Man (Woman) in the middle attack

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RSA Algorithm

• How does RSA work? • Class Participation Exercise on RSA

application• Why does RSA work?

(See additional handouts for answers)

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Example to illustrate RSA Algorithm Participation Exercise

• Background:– Bob has selected the prime numbers p and q as 5 and 7

respectively.

– Bob has selected e to be the number 5.

– Alice and Bob interpret each letter in the English alphabet as a number between 1 and 26. That is, a = 1, b = 2, …, n = 14,…, z = 26.

– Alice wishes to send the plaintext “love” to Bob, after encrypting using RSA.

• Questions:– Compute Bob’s public key using RSA. – Determine Alice’s cipher text using RSA algorithm.

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RSA Algorithm

• Even for small p and q, as seen in the participation exercise, we had to deal with extremely large numbers.

• If we follow the suggestion of RSA labs and select p and q to be several hundred bits long, then the following practical issues come to mind:– How to choose large prime numbers p and q?– How to choose e and d?– How to perform exponentiation with large numbers?

(For those who are interested in this area, refer to Kaufman 1995 for answers to the above mentioned questions).

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RSA and DES/AES

• DES is at least 100 times faster than RSA.

• In practice, RSA is often used in combination with DES or AES. How?

(Alice encrypts DES key with Bob’s public key. Bob decrypts and obtains DES key with his private key. The data is encrypted using DES key, which now both Alice and Bob have access to in order to encrypt/decrypt data).

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Security of RSA

• The security of RSA relies on the fact that there are no known algorithms for quickly factoring a number (n), into the primes p and q. If one knew p and q, then given e, one could then easily compute the secret key d. It is not known whether or not there exist fast algorithms for factoring a number, and in this sense the security of RSA is not guaranteed.

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Authentication

• ap 1.0

• ap 2.0

• ap 3.0

• ap 3.1

• ap 4.0

• ap 5.0

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Authentication

• ap 1.0– Alice announces to Bob, “I am Alice.”

• Trudy could have sent this message.

• ap 2.0– Alice announces to Bob, “I am Alice”, and

asks Bob to authenticate her by matching source IP (in IP header) with Alice’s IP.

• Trudy could have sent this message if she had done IP spoofing.

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Authentication

• ap 3.0– Alice announces to Bob, “I am Alice”, and asks Bob to

authenticate her by verifying her plaintext password. • Trudy may have already eavesdropped earlier, and have

stolen Alice’s plaintext password during an earlier conversation between Alice and Bob. Now, Trudy could send the message, “I am Alice” by using Alice’s plaintext password.

• ap 3.1– Alice announces to Bob, “I am Alice”, and asks Bob to

authenticate her by verifying her encrypted password, which is kept the same for different communication sessions between Bob and Alice.

• Same disadvantage mentioned in ap 3.0 still exists. Note that Trudy need not decrypt the password. She could still eavesdrop, steal encrypted password, and then perform a “playback attack” on Bob.

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Authentication

• ap 4.0– Alice announces to Bob, “I am Alice.” – Bob sends a plaintext nonce (= r) to Alice.

• Note that nonce is a one time value that is specific to that communication session. It is not repeated again in another session. So “playback attack” is not possible.

– Alice resends same nonce back to Bob but this time nonce is encrypted with symmetric key used by Alice and Bob.

– Bob decrypts nonce using symmetric key. If decrypted nonce equals the nonce he sent Alice earlier (i.e. decrypted nonce = r) , then Alice is authenticated.

– However, this implies that Alice and Bob must have decided upon and exchanged their symmetric key.

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Authentication

• ap 5.0– Alice announces to Bob, “I am Alice.” – Bob sends a plaintext nonce (= r) to Alice.

• Since nonce is a one-time value, “playback attack” is not possible.

– Alice resends same nonce back to Bob but this time nonce is encrypted with Alice’s private key.

– Bob decrypts nonce using Alice’s public key. If decrypted nonce equals the nonce he sent Alice earlier (i.e. decrypted nonce = r) , then Alice is authenticated.

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Exchanging Public Keys

• Why should public key be publicly available?

• Wouldn’t it be better for Alice and Bob to exchange their respective public keys via e-mail, after authenticating each other?– Due to possibility of “man (woman) in the

middle attack.”

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Man (Woman) in the Middle Attack

• Alice transmits, “I am Alice.”• Trudy (alias Eve) eavesdrops. • Bob sends a nonce = r. • Trudy intercepts nonce, and

sends Bob encrypted nonce (encrypted using her private key).

• Bob sends a message to Alice asking her for a public key.

• Trudy intercepts message, and sends Bob Trudy’s public key.

• Bob decrypts nonce with Trudy’s public key (thinking that he is using Alice’s public key), and inadvertently authenticates Trudy.

• While Bob is encrypting new data using Trudy’s public key, Trudy is busy posing as Bob to Alice. In particular, – Trudy transmits Bob’s

nonce to Alice– Alice transmits encrypted

nonce (encrypted using Alice’s private key).

– Trudy intercepts encrypted nonce, and asks Alice for her public key.

– Alice sends her public key

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Man (Woman) in the Middle Attack

• Bob sends encrypted data (encrypted using Trudy’s public key)

• Trudy decrypts using her private key, and finds out Bob’s plain text.

• Trudy encrypts Bob’s plain text using Alice’s public key.

• Trudy transmits encrypted text to Alice. • Alice decrypts using her private key, and finds out

Bob’s plain text. • Alice and Bob are happy that they have had a

secure communication. They are ignorant of the fact that Trudy has intercepted and decrypted Bob’s message to Alice.

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Public Key Certification

• PK cryptography – possible for two entities to exchange secret messages without having to exchange secret keys.

• Communicating entities have to exchange public keys (without being subject to “man in the middle attack”).

• Binding a public key to a particular entity is typically done by a Certification Authority (CA).

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Certification Authority

• A CA verifies that an entity is who it claims to be.

• After verification, CA creates a certificate that binds the public key to appropriate entity.

• Certificate – includes a public key– includes globally unique identifying information

about owner of the public key– Is digitally signed by CA

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Digital Signatures and Message Digests

• Assume Bob wants to digitally sign a “document,” m.

• Bob’s digital signature could be KB- (m)

• Due to complexity of RSA, digital signatures are applied to “fingerprints” instead of being applied to message m.

• Fingerprint – H(m) – where H denotes a “hash algorithm”

• Bob’s digital signature is KB- (H(m))

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Message Digests

• Message Digest (Hash) algorithms:– MD5; SHA-1; SHA-224;-256;-384;-512

• Secure Hash Algorithm is a U.S. federal standard

• Required for use whenever a secure message digest algorithm is required for federal applications

• Produces a 160-bit message digest.

• Longer the output length, the more secure SHA-1

• SHA-224, SHA-256, SHA-384, and SHA-512, (which despite the similarity of names), are actually fairly different algorithms to SHA-1 and have much wider safety margins.

Management’s Role in Security

A framework to help managers understand that security rests on three cornerstones

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Three Cornerstones

• Technology

• Organization

• Critical Infrastructure– Management should provide strong

leadership in all three areas.

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Cornerstone: Technology

• Have an understanding/appreciation of technology– Firewalls– IDS/IPS systems– Antivirus/Security Patches– Physical security– Client/Server/Perimeter Security; Secure VPNs– Evaluation of potential technology acquisitions

based on their impact on security– Symmetric and Public Key Cryptography

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Example: DDoS attack on iPremier Company

• IPremier– Sells luxury and rare high priced items on

Internet– Survived dot com implosion– Customers have good credit history with high

spending limits – Experienced a DDoS on Web Server– Ha Ha Ha! e-mails received by Help Desk

• Problems at Colocation facility: Qdata • iPremier employees could not get access to

Qdata’s Network Operations Center (NOC)

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Questions

• About Qdata:• Although an early entrant in the industry, Qdata lost

any prospect of market leadership• Had not been quick to invest in advance technology• Had experienced difficulty in retaining qualified staff

• Questions:– If you were the CIO, how would you react to this

situation? – What implications does this situation have for the

iPremier company?

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iPremier Example (Continued)

• Unable to determine extent of damage (firewall penetrated? How deep is the penetration?)

• Unable to determine if customer data was stolen (CIO’s main immediate concern)

• Unable to track (in a reasonable time frame) where ‘Ha, ha, ha’ e-mails received by “support” folks are originating

– Even if e-mail is tracked eventually – leads to another “Zombie

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iPremier’s Response to Attack: Very Poor

• Try to shut down traffic from “Zombies” – didn’t work – for every zombie that was shut down – two new zombies joined the “party” automatically

• Shut down Web Server?

• Cost of downtime?

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Imperative Need for Secure CommunicationCost of downtime

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• Unable to determine if they should “disconnect the communication lines”

• initially CIO and CTO had discussion - may lose logging data that could help them figure out what happened (preserving evidence to find root cause of problem; and what to disclose publicly);

• later concluded that detailed logs have not been enabled

• Unable to determine if they should call “Seattle Police” or “FBI”?

iPremier’s Response to Attack: Very Poor

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• How to handle PR (before info about security breach leaks out)?

• Unable to decide if all systems need to be rebuilt • Worst is over? Damage has been done?• Attack stopped after about 75 minutes – without any

intervention from iPremier or from Qdata!• FBI Calls iPremier?• Would system rebuild imply wiping out any remaining

proof of iPremier’s innocence?

iPremier’s Response to Attack: Very Poor

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Some Business Implications for IPremier

• Web server unavailable to legitimate customers

• Cost of downtime?• Bad reputation for the business

• Lost customers• Loss of customer goodwill• Legal issues if customer data was

compromised

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Some Business Implications for IPremier

• Impact on stock price• Unknown damages to the

network/business?• What if there was another attack?

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Cornerstone: Organization

• Organizational characteristics – typically under the control of organization– Structure– Business environment– Culture– Policies and Responses– Standard Operating Procedures– Education, Training, and Awareness

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Management’s Role in Security

• Realize that total/perfect security is a myth

• Act appropriately, recognizing that security rests on three cornerstones

• Critical Asset Identification

• Initial Risk Assessment

• Risk Assessment as a continuous process

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Management’s Role in Security

• Creating a security team

• Initiate and actively participate in planning/design/documentation/ testing of security policy

• Actively involved in establishing standard operating procedures

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Management’s Role in Security

• Developing and maintaining an appropriate organizational culture

• Ensure employees are educated and trained regarding importance of following security policy

• Have an understanding of what each security tool proposed by IT team can do or cannot do

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Management’s Role in Security

• Have a good control environment– Physical controls– Data/Content control– Implementation control (outsourcing)– Operations/Administrative Control– Application Controls specific to individual

system components/applications

(e.g., Limiting e-mail attachments)

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Cornerstone: Critical Infrastructure

• Infrastructure that are so vital that their damage or destruction would have a debilitating impact on the physical or economic security of the country– Telecommunications– Banking – Energy

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Why should government/academic institutions/industry collaborate?

• In each other’s interestCI in large part is owned by the private sector, used by both private and public sectors, and protected in large part by public sector.

• Need to discuss problems and exchange ideas and solutions to cyber attacks/misuse

• Resource/cost/information sharing• Opportunity to play a role in the evolution of “best

practices”• Help shape legal and government policies in areas

of mutual concerns; Appropriate guidance for rapid additional protection measures

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CERT Source: http://www.us-cert.gov/

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What does CERT do?

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Imperative Need for Secure CommunicationReported Security Incidents up to 1995

Source: CERT.ORG

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Reported Security Incidents 1995 – 2003 Source: http://www.cert.org/present/cert-overview-trends/module-1.pdf

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Why have cyber attacks been on the rise?Some reasons

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Management’s Role in Security

• Recognize that security requires an end-to-end view of business processes

• Achieve a balanced approach to security – one that does not solely focus on technological solutions

• Recognize that security is a socio-technical issue, and requires strong leadership from management

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Management’s Role in Security

• Management ties everything together

• Responsibility

• Ownership

TechnologyInfrastructure

Organization

Management

Security is a Mindset, not a service. It must be a part of all decisions and implementations.

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• Apply the Dutta/McCrohan framework and help iPremier’s management react appropriately to the security incident.