Lecture 3 Basic Security Concepts cont.

1. Lecture 3 Basic Security Concepts cont.

2. Homework 1. • Score: 10 points • Due: September 12, 2013 2:00 am via dropbox • Last day to submit with 4%/day penalty: September 23, 2013 2:00 am via dropbox •  From C. P. Pfleeger and S. L. Pfleeger: Security in Computing, 4th Edition answer the following questions: • Chapter 1: 1, 10, 15 • Chapter 2: 13, 18, 34 • Grading: Answer all of the questions. Only one of them will be chosen by the instructor to be graded. • Solutions for all questions will be posted online and discussed in class after the last day to submit date. CSCE 522 - Farkas

3. Research Project • Project information: http://cse.sc.edu/~farkas/csce522-2013/project-2013.htm • Step 1 • Identifying research interest • Form groups of 2-4 students CSCE 522 - Farkas

4. Project Information • Discussion on Student preferences • What do you like to work on? • E.g., application development, operating systems, databases, hardware design, robotics, game development, etc. • What are the security problems in your area of interest? • E.g., multilevel secure operating systems, access control in databases, remote controlled robots, etc. • How much your group can do within 1 semester? • E.g., need to choose a problem that can be addressed within 12 weeks (including any background research, research, development, and writing reports) • Be as specific as possible! 4 CSCE 522 - Farkas

5. Types of Attacks (1) • Interruption – an asset is destroyed, unavailable or unusable (availability) • Interception – unauthorized party gains access to an asset (confidentiality) • Modification – unauthorized party tampers with asset (integrity) • Fabrication – unauthorized party inserts counterfeit object into the system (authenticity) • Denial – person denies taking an action (authenticity) CSCE 522 - Farkas

6. Types of Attacks (2) • Passive attacks: • Eavesdropping • Monitoring • Active attacks: • Masquerade – one entity pretends to be a different entity • Replay – passive capture of information and its retransmission • Modification of messages – legitimate message is altered • Denial of service – prevents normal use of resources CSCE 522 - Farkas

7. Malicious Attacks Method: skills, knowledge, tools, information, etc. Opportunity: time and access Motive: reason to perform the action How can defense influence these aspects of attacks? CSCE 522 - Farkas

8. Computer Criminals • Amateurs: regular users, who exploit the vulnerabilities of the computer system • Motivation: easy access to vulnerable resources • Crackers: attempt to access computing facilities for which they do not have the authorization • Motivation: enjoy challenge, curiosity • Career criminals: professionals who understand the computer system and its vulnerabilities • Motivation: personal gain (e.g., financial) CSCE 522 - Farkas

9. Methods of Defense • Prevent: block attack • Deter: make the attack harder • Deflect: make other targets more attractive • Detect: identify misuse • Tolerate: function under attack • Recover: restore to correct state CSCE 522 - Farkas

10. Information Security Planning • Organization Analysis • Risk management • Mitigation approaches and their costs • Security policy • Implementation and testing • Security training and awareness CSCE 522 - Farkas

11. Carry Out Fixes and Validate Identify Business and Technical Risks Define Risk Mitigation Strategy Synthesize and Rank Risks Measurement and Reporting Risk Management Framework (Business Context) Understand Business Context CSCE 522 - Farkas

12. Cryptography 1 Project Topics Cyber Attacks Cryptography Terminology Secret-Key Encryption

13. Reading Assignment • Reading assignments for this lecture Required: • Pfleeger: Ch 2 Recommended: • C. Dupuis, A Short History of Cryptography, http://jproc.ca/crypto/crypto_hist.html • Navajo Code Talkers: World War II Fact Sheet, http://www.history.navy.mil/faqs/faq61-2.htm Interesting: • U.S. always ends up regulating new technologies for public safety; the Internet is no exception, Homeland Security News Wire, http://www.homelandsecuritynewswire.com/bull20120829-u-s-always-ends-up-regulating-new-technologies-for-public-safety-the-internet-is-no-exception , 08/29/2012 CSCE 522 - Farkas

14. Snooper Insecure channel Recipient Sender Insecure communications Confidential CSCE 522 - Farkas

15. Cryptographic Protocols • Messages should be transmitted to destination • Only the recipient should see it • Only the recipient should get it • Proof of the sender’s identity • Message shouldn’t be corrupted in transit • Message should be sent/received once only CSCE 522 - Farkas

16. Terminology • Plaintext (cleartext): a message in its original form • Ciphertext (cyphertext): an encrypted message • Encryption: transformation of a message to hide its meaning • Cipher: cryptographic algorithm. A mathematical function used for encryption (encryption algorithm) and decryption (decryption algorithm). CSCE 522 - Farkas

17. Terminology • Decryption: recovering meaning from ciphertext • Cryptography: art and science of keeping messages secure • Cryptanalysis: art and science of breaking ciphertext • Cryptology: study of both cryptography and cryptanalysis CSCE 522 - Farkas

18. Encryption and Decryption Plaintext Plaintext Ciphertext Encryption • Additional requirements: • Authentication • Between communicating parties • Third-party authentication • Non-repudiation • Integrity verification • Key distribution • Secret key (secure distribution) • Public key (reliable distribution) Decryption CSCE 522 - Farkas

19. Conventional (Secret Key) Cryptosystem Plaintext Ciphertext Plaintext Encryption Decryption Sender Recipient K C=E(K,M) M=D(K,C) K needs secure channel CSCE 522 - Farkas

20. Public Key Cryptosystem Recipient’s public Key (Kpub) Recipient’s private Key (Kpriv) Plaintext Ciphertext Plaintext Encryption Decryption Sender Recipient C=E(Kpub,M) M=D(Kpriv,C) Kpubneeds reliable channel CSCE 522 - Farkas

21. Security Objectives How can cryptography support these objectives? Confidentiality Integrity Availability Authenticity Non-repudiation CSCE 522 - Farkas

22. Security Objectives • Confidentiality: Hiding message/file content • Secret key, public key encryption • Integrity: Detecting modification • Hash function • Availability: Not much – hiding existence of data • Secret key, public key encryption • Authenticity: Verify origin • Public key encryption • Non-repudiation: Verify activity • Public key encryption CSCE 522 - Farkas CSCE 522 - Farkas 22

23. Cryptanalysis Cryptanalyst’s goal: • Break message • Break key • Break algorithm CSCE 522 - Farkas

24. Taxonomy of Attacks • Ciphertext-only attack: attacker has ciphertext for messages encrypted with K. Deduce keys and/or plaintext messages. • Known plaintext attack: attacker additionally knows the plaintext of the messages. Deduce keys or a decryption algorithm. • Chosen plaintext attack: attacker can obtain the ciphertext for selected plaintext messages. Deduce as above. • Chosen ciphertext attack: attacker can obtain decrypted (plaintext) versions of selected ciphertext. Deduce as above. CSCE 522 - Farkas

25. Breakable versus Practically breakable • Unconditionally secure: impossible to decrypt. No amount of ciphertext will enable a cryptanalyst to obtain the plaintext • Computationally secure: an algorithm that is not breakable in practice based on worst case scenario • Breakable: all algorithms (except one-time pad) are theoretically breakable CSCE 522 - Farkas

26. What makes a good cryptosystem? • A good cryptosystem is one whose security does not depend upon the secrecy of the algorithm. • From Bruce Schneier: • “Good cryptographers rely on peer review to separate the good algorithms from the bad.'' CSCE 522 - Farkas

27. Secret Key Cryptosystem Plaintext Ciphertext Plaintext Encryption Decryption Sender Recipient K C=E(K,M) M=D(K,C) K needs secure channel CSCE 522 - Farkas

28. Secret Key Cryptosystem Vulnerabilities (1 Passive Attacker (Eavesdropper) • Obtain and/or guess key and cryptosystem use these to decrypt messages • Capture text in transit and try a ciphertext-only attack to obtain plaintext. CSCE 522 - Farkas

29. Secret Key Cryptosystem Vulnerabilities Active Attacker • Break communication channel (denial of service) • Obtain and/or guess key and cryptosystem and use these to send fake messages CSCE 522 - Farkas

30. Inherent Weaknesses of Symmetric Cryptography • Key distribution must be done secretly (difficult when parties are geographically distant, or don't know each other) • Need a key for each pair of users • n users need n*(n-1)/2 keys • If the secret key (and cryptosystem) is compromised, the adversary will be able to decrypt all traffic and produce fake messages CSCE 522 - Farkas

31. Basic Encryption Techniques • Substitution • Permutation • Combinations and iterations of these CSCE 522 - Farkas

32. Next Class • Substitution and Transposition • Characterization of good encryption algorithms CSCE 522 - Farkas