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Security Matters. V.T. Raja, Ph.D., Oregon State University. Security Matters. Outline Summary Example to illustrate RSA Algorithm A framework to help managers understand their role in security . Summary from first lecture on Security. Characteristics of Secure Communication

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Security matters

Security Matters

V.T. Raja, Ph.D.,

Oregon State University

Security matters1
Security Matters

  • Outline

    • Summary

    • Example to illustrate RSA Algorithm

    • A framework to help managers understand their role in security

Summary from first lecture on security
Summary from first lecture on Security

  • Characteristics of Secure Communication

  • Perfect security – a myth or a reality?

  • Ciphers and Cryptography

  • Authentication (ap1.0 - ap5.0)


  • Ciphers

    • Caesar, Monoalphabetic, Polyalphabetic

  • Symmetric Key Cryptography (SKC)

    • Basic idea of SKC

    • Notation for symmetric key

    • Some popular SKC algorithms

    • Sharing of symmetric key

Public key cryptography pkc
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

Rsa algorithm
RSA Algorithm

  • How does RSA work?

  • Class Participation Exercise on RSA application

  • Why does RSA work?

    (See additional handouts for answers)

Example to illustrate rsa algorithm participation exercise
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.

Rsa algorithm1
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).

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).

Security of rsa
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.


  • ap 1.0

  • ap 2.0

  • ap 3.0

  • ap 3.1

  • ap 4.0

  • ap 5.0


  • 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.


  • 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.


  • 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.


  • 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.

Exchanging public keys
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.”

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

Man (Woman) in the Middle Attack

Man woman in the middle attack1
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.

Public key certification
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).

Certification authority
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

Digital signatures and message digests
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))

Message digests
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

Management’s Role in Security

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

Three cornerstones
Three Cornerstones

  • Technology

  • Organization

  • Critical Infrastructure

    • Management should provide strong leadership in all three areas.

Cornerstone technology
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

Example ddos attack on ipremier company
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)


  • 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?

  • Ipremier example continued
    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

    Ipremier s response to attack very poor
    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?

    Ipremier s response to attack very poor1
    iPremier’s Response to Attack: Very Poor

    • 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 poor2
    iPremier’s Response to Attack: Very Poor

    • 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?

    Some business implications for ipremier
    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

    Some business implications for ipremier1
    Some Business Implications for IPremier

    • Impact on stock price

    • Unknown damages to the network/business?

    • What if there was another attack?

    Cornerstone organization
    Cornerstone: Organization

    • Organizational characteristics – typically under the control of organization

      • Structure

      • Business environment

      • Culture

      • Policies and Responses

      • Standard Operating Procedures

      • Education, Training, and Awareness

    Management s role in security1
    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

    Management s role in security2
    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

    Management s role in security3
    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

    Management s role in security4
    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)

    Cornerstone critical infrastructure
    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

    Why should government academic institutions industry collaborate
    Why should government/academic institutions/industry collaborate?

    • In each other’s interest

      CI 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

    Cert source http www us cert gov
    CERT collaborate? Source:

    What does cert do
    What does CERT do? collaborate?

    Imperative need for secure communication reported security incidents up to 1995 source cert org
    Imperative Need for Secure Communication collaborate?Reported Security Incidents up to 1995Source: CERT.ORG

    Reported Security Incidents 1995 – 2003 collaborate?Source:

    Management s role in security5
    Management’s Role in Security collaborate?

    • 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

    Management s role in security6

    Security collaborate?








    Management’s Role in Security

    • Management ties everything together

    • Responsibility

    • Ownership

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

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