lecture 3 basic security concepts cont

Lecture 3

Basic Security Concepts cont.

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 2

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Research Project

Project information: http://cse.sc.edu/~farkas/csce522-2013/project-2013.htm

Step 1 Identifying research interestForm groups of 2-4 students

CSCE 522 - Farkas

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

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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)

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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

Malicious Attacks

Method: skills, knowledge, tools, information, etc.

Opportunity: time and accessMotive: reason to perform the action

How can defense influence these aspects of attacks?

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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 9Lecture 1

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

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Information Security Planning Organization Analysis Risk management Mitigation approaches and their costs Security policy Implementation and testing Security training and awareness


Risk Management Framework(Business Context)

Understand BusinessContext

Identify Business and Technical Risks

Synthesize and RankRisks

Define RiskMitigation Strategy

Carry Out Fixesand Validate

Measurement and Reporting

Cryptography 1

Project Topics Cyber Attacks Cryptography Terminology Secret-Key Encryption


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


Insecure communications

Sender

Snooper

Recipient

Insecure channel

Confidential


Cryptographic Protocols

Messages should be transmitted to destinationMessages should be transmitted to destination Only the recipient should see itOnly the recipient should see it Only the recipient should get itOnly the recipient should get it Proof of the sender’s identityProof of the sender’s identity Message shouldn’t be corrupted in transitMessage shouldn’t be corrupted in transit Message should be sent/received once onlyMessage should be sent/received once only


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).


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


Encryption and Decryption

Plaintext PlaintextEncryption Decryption

Ciphertext

Additional requirements:• Authentication

• Between communicating parties• Third-party authentication

• Non-repudiation• Integrity verification• Key distribution

• Secret key (secure distribution)• Public key (reliable distribution)


Conventional (Secret Key) Cryptosystem

Encryption DecryptionPlaintext PlaintextCiphertext

K

Sender Recipient

C=E(K,M)M=D(K,C)

K needs secure channel


Public Key Cryptosystem


Sender Recipient

C=E(Kpub,M)M=D(Kpriv,C)

Recipient’s public Key (Kpub)

Recipient’s private Key (Kpriv)

Kpub needs reliable channel

Security Objectives

Confidentiality Integrity Availability Authenticity Non-repudiation


How can cryptography support these objectives?


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



CryptanalysisCryptanalyst’s goal:

Break messageBreak keyBreak algorithm


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.


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


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.''


Secret Key Cryptosystem


K

Sender Recipient

C=E(K,M)M=D(K,C)

K needs secure channel


Secret Key Cryptosystem Vulnerabilities (1

Passive Attacker (Eavesdropper)Obtain and/or guess key and cryptosystem

use these to decrypt messagesCapture text in transit and try a ciphertext-

only attack to obtain plaintext.


Active AttackerBreak communication channel (denial of

service)Obtain and/or guess key and cryptosystem

and use these to send fake messages

Secret Key Cryptosystem Vulnerabilities


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


Basic Encryption Techniques

Substitution Permutation Combinations and iterations of these


Next Class

Substitution and TranspositionCharacterization of good encryption

algorithms

lecture 3 basic security concepts cont

Documents

passive attacks

types of attacks

aspects of attacks

access control

easy access

normal use of resources

background research

security problems