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SFS Workshop 2012

May 21, 2012SFS Summer Workshop at

UT Chattanooga

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Program Goals

• Build capacity in IA education through faculty summer workshops– Increased faculty interest and participation in IA

education. – Increased number of courses and institutions

adopting the hands-on exercises and case studies • Develop student mastery of and interest in IA

topics• Provide a platform of sharing and collaboration Is

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Topics and Speakers

• Cryptography, Access Control, Cloud Computing, Forensics, and Security Ethics by Li Yang, Joseph Kizza and Kathy Winters from UT Chattanooga

• Security Management, Buffer-over-flow, Firewall by Xiaohong (Dorothy) Yuan and Ken Williams from North Carolina A&T State University

• Web Security and Network Security by Bill Chu from University of North Carolina at Charlotte

• Virtualization and Security Hands-on Learning by Vincent Nestler

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Cryptography Hands-on Learning

• CrypTool• Programming

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Overview of Security Services

Data confidentiality protects data from disclosure attack.

Data integrity protect data from modification, insertion, deletion, and replaying attacks.

Authentication provides proof of sender, or receiver, or source of the data.

Nonrepudiation protects against repudiation by either the sender to the reveiver.

Access control provides protection again unauthorized access to data.

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Cryptography

• Symmetric Cryptography• Public Key Cryptography• Hash Function• Digital Signature• Key Management

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Symmetric Key Ciphers• Traditional Symmetric Key ciphers

– A substitution cipher replaces one symbol with another.

– A transposition cipher reorders symbols.• Modern Symmetric-key Ciphers

– Stream ciphers operate on the plaintext a single bit (or sometimes byte) at a time

– Block ciphers operate on the plaintext in groups of bits. The groups of bits are called blocks.

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Playfair Encryption

• Let us generate keypad using keyword “CHATTANOOGA” and encrypt the plaintext “Cryptography” using the keypad.

• CR AP, YP SV, TP CD• Good exercises for two-dimension arrays

Example: Lab on Playfair encryption

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DES• DES was adopted as a US federal standard for

commercial encryption in 1975.• The S-Boxes design provides confusion and diffusion

of bits from each round to the next. • The P-Boxes provide diffusion of bits.• DES uses sixteen rounds of Feistel ciphers. the cipher

text is thoroughly a random function of plaintext and cipher text.

• Visualization “Indiv. Procedures\Visualization of Algorithms\DES”

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Weaknesses in DES

Critics have found some weaknesses in DES.Weaknesses in Cipher Design1. Weaknesses in S-boxes• Two specifically chosen inputs to an S-box can create same output2. Weaknesses in P-boxes• initial and final permutations have no security benefits• the first and fourth bits of every 4-bit series are repeated3. Weaknesses in Key• Weak keys create same 16 round keys• Semi-weak keys create 2 different round keys• Possible weak keys create 4 distinct round keys• Key complement

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Double encryption and decryption with a weak key

PPEE kk ))((Example: Lab on Weak DES keys

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AES

• The Advanced Encryption Standard (AES) is a symmetric-key block cipher published by the National Institute of Standards and Technology (NIST) in December 2001.

• AES has defined three versions, with 10, 12, and 14 rounds.

• Each version uses a different cipher key size (128, 192, or 256), but the round keys are always 128 bits.

• Visualization: “Indiv. Procedures\Visualization of Algorithms\AES\Rijindael Animation”

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Modes of operation

• How to encrypt large messages?– Partition into n-bit blocks– Choose mode of operation

• Modes of operation have been devised to encipher text of any size employing either DES or AES.

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Evaluation criteria of modes• Identical messages

– under which conditions cipher text of two identical messages are the same

• Chaining dependencies – how adjacent plaintext blocks affect encryption of a

plaintext block • Error propagation

– resistance to channel noise• Efficiency

– preprocessing– parallelization: random access

• Example: Lab on modes of operation

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Cryptanalysis

As cryptography is the science and art of creating secret codes, cryptanalysis is the science and art of breaking those codes.

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Cipher text-Only Attack

Cipher text + algorithm key and the plaintext

• Brute-Force attack: exhaustive key search attack

•Statistical attack: benefit from inherent characteristics of the plaintext language. E.g. E is the most frequently used letter. Example: Lab on Frequency Analysis

•Pattern attack: discover pattern in cipher text.

•Example: Labs on binary addition and XOR encryption

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Hash Function• A cryptographic hash function takes a message of arbitrary

length and creates a message digest of fixed length. The goal is to ensure integrity of message.

• Resistance to three attacks– Preimage attack: find M’ such that that D=h(M’) given

D=h(M)– Second Preimage Attack: find M’ such that h(M’)=D given D

and M– Collision Attack: Find two messages M and M’ such that

H(M)=h(M’)• Using multiple rounds of encryption or compression

Cryptographic APIs

Cryptlib(http://www.cryptlib.com/)

– easy to use– free for

noncommercial use

OpenSSL(http://www.openssl.org)

– poorly documented– open source– popular

Crypto++(http://www.cryptopp.com/)

– C++ library– open source

BSAFE (http://www.rsa.com/node.aspx?id=1204)

– well documented, Java, C/C++– most popular commercial library– Was commercial SDK from RSA– free from 2009 under RSA Share

Project

Cryptographic APIs

Cryptix: JCA, JCE– open source Java library, C# library– http://www.bouncycastle.org/java.html

Python Cryptographic Toolkit– open source crypt, hash, rand modules– http://www.amk.ca/python/code/crypto

Crypt:: CPAN modules for Perl– well documented– many different libraries

Supported Ciphers

1. Range of MAC algorithmsAlmost all include MD5, SHA-1

2. Range of symmetric algorithmsAlmost all include AES, DES

3. Range of public key algorithmsAlmost all include RSA, Diffie-Hellman, DSA

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Work on labs (1)

From 9:15am to 10:15am• 1.1 Encryption using classical techniques -- Playfair• 1.2 frequency analysis• 2.1 Encryption using binary addition• 2.2 Encryption using binary Exclusive-OR (XOR)• 2.3 Triple DES with CBC mode and Weak DES keys• 2.4 Testing different modes in symmetric ciphers• 4.1 Hash generation and sensitivity of hash functions to

plaintext modifications• 4.2 Hash function

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Coffee Break(10:15-10:45am)

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Public key cryptography

need K ( ) and K ( ) such thatB B. .

given public key K , it should be impossible to compute private key K B

B

Requirements:

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RSA: Rivest, Shamir, Adleman algorithm

+ -

K (K (m)) = m BB

- +

+

-

• Public key cryptography uses two separate keys: one private and one public.

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RSA: Choosing keys1. Choose two large prime numbers p, q. (e.g., 1024 bits each)

2. Compute n = pq, z = (p-1)(q-1)

3. Choose e (with e<n) that has no common factors with z. (e, z are “relatively prime”).

4. Choose d such that ed-1 is exactly divisible by z. (in other words: ed mod z = 1 ).

5. Public key is (n,e). Private key is (n,d).

K B+ K B

-

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Attacks on RSA – Factorization Attack No devastating attacks on RSA have been yet discovered. Bob selects p and q and calculate n=p*q. n is public but p

and q are secret. If Eve can factor n and obtain p and q, she can calculate private d from public e by

))1)(1mod((1 qped However, none of existing factorization algorithms can

factor a large integer with polynomial time complexity. To be secure, RSA presently requires that n should be

more than 300 decimal digits, which means that the modulus must be at least 1024 bits.

Example: Lab on 3.1

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Short message attacks

• Known: Cipher text, RSA algorithm• Unknown: plaintext, key• Short message attack – if it is known that Alice

is sending a four-digit number to Bob, Eve can easily try plaintext numbers from 0000 to 9999 to find the plaintext.

• Example: Lab 3.2 on short message attack

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Optimal asymmetric encryption padding (OAEP)

• P = P1 || P2, where P1 is the masked version of the padded message M; P2 is sent to allow Bob to find the mask

• Encryption– Pad the plaintext to make m-bit message M, if M is less

than m-bit – Choose a random number r of k-bits. (used only once)– Use one-way function G that inputs r-bit integer and

outputs m-bit integer. This is the mask. – P1 = M G(r) – P2 = H(P1) r, function H inputs m-bit and outputs k-bit– C = E(P1 || P2). Use RSA encryption here.

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OAEP

• Decryption– P = D (P1 || P2)– Bob first recreates the value of r:

H(P1) P2 = H(P1) H(P1) r = r– Bob recreates msg:

G(r) P1 = G(r) G(r) M = M

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Timing attacks• RSA fast-exponential algorithm uses

– only squaring if the corresponding bit in the private exponent d is 0. requires shorter time to decrypt.

– Both squaring and multiplication if the corresponding bit is 1. requires longer time to decrypt

• This timing difference allows Eve to find the value of bits in d, one by one.

• Example: lab 3.3 timing attack

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Digital Signature• The sender uses a signing algorithm to sign the message.

The message and the signature are sent to the receiver. The receiver receives the message and the signature and applies the verifying algorithm to the combination. If the result is true, the message is accepted; otherwise, it is rejected.

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Kerberos

• An authentication solution and a way to manage keys in symmetric ciphers

• Will be discussed on Tuesday/Wednesday

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IA resources and projects (1)

• SEED: Developing Instructional Laboratories for Computer SEcurity Education @ Syracuse University http://www.cis.syr.edu/~wedu/seed/index.html

• SWEET: Secure Web Development Teaching Modules @ Pace University http://csis.pace.edu/~lchen/sweet/

• Security Injection@ Towson Universityhttp://triton.towson.edu/~cssecinj/secinj/

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IA resources and projects (2)

• National Initiative Cybersecurity Education (NICE): http://csrc.nist.gov/nice/

• DETER Network Security Testbedhttp://www.isi.deterlab.net/index.php3

• The Open Web Application Security Project (OWASP) http://owasp.com/index.php/Main_Page

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Work on Labs II

From 10:45am-11:45pm• 3.1 RSA encryption and attacks• 3.2 RSA Short message attacks and padding• 3.3 RSA timing attacks• 5.1 Digital signature visualization• 5.2 RSA signature• 5.3 Attack on digital signature/hash collision• 5.4 Digital signature (programming)