Introduction to Information Security Lecture 2: Quick Overview on Information Security
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Transcript of Introduction to Information Security Lecture 2: Quick Overview on Information Security
Introduction to Information Security
Lecture 2: Quick Overview on Information Security
2009. 6.
1961
•중앙정보부 (현 국가정보원) 통신보안 업무 개시
1964
•보안업무규정(대통령령) 및 시행규칙(대통령 훈령) 제정
1980
•국가정보원법 제정
1981
•정보 및 보안업무기획, 조정규정(대통령령) 제정
•국방과학연구소(ADD) 샛별부 신설
1983
•한국전자통신연구원(ETRI) 부호기술부 신설
1989
•국내최초 암호학술대회 WISC 개최
1990
•한국(통신)정보보호학회 창립
History of Information Security (1/3)
‘81:IACR 창립 및 Crypto 개최
‘82:EuroCrypt 최초개최
‘91:AsiaCrypt 최초개최
출처 :2009 년정보보호백서
1996
•정보통신부 민간 정보보호 담당과 신설, 한국정보보호진흥원(KISA) 설립
1998
•최초 국산 블록암호 알고리즘 SEED 개발, 정보보호시스템 평가인증 시행 (K-ISA)
1999
•국가정보보안기본지침 제정, 을지연습 사이버전 모의훈련 실시
2000
•국가보안기술연구소(NSRI) 설립
2001
•정보통신기반보호법 및 전자정부법 제정
2002
•국가정보보호백서 발간
•정보보안연합회(NISA) 창설
Asiacrypt’96 국내최초개최
2000: AES 탄생
출처 :2009 년 정보보호백서
History of Information Security (2/3)
2003
•1.25 인터넷 대란 발생, KISA 인터넷침해사고대응지원센터 설립
•블록암호 알고리즘 ARIA 개발
2004
•국가정보원, 국가사이버안전센터(NCSC) 설립
•국가위기관리기본지침 및 국가위기관리매뉴얼 제정
2005
•국가사이버안전관리규정 (대통령 훈령) 및 국가 사이버안전 매뉴얼 제정
2006
•CCRA 가입
•국가위기대응통합연습 실시
2007
•국가정보보호백서 발간
•정보보호제품 민간 평가기관 지정
2008
•행정, 국방, 에너지, 교통 등 10대 부분 보안관제센터 설립 완료•범
국가 보안관제체계 구축
Asiacrypt’04 국내 2 회개최
출처 :2009 년정보보호백서
History of Information Security (13/3)
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Evolution of Attack
1. From a hobby to a profitable industry
2. From annoying to de-structive
3. From playing to steal-ing
4. From simplicity to complexity
Hacker’s Motivation
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Efficient work style,competitiveness
2000
Users
National security,calculation use
Reliability of systems
E-commerceEconomic infrastructure
Lifelines for society, economy, and daily life
Exclusive systems Big, host types C/S types PC, Internet Mobile & Ubiquitous
Government
Banking, transportation, energy sectors
Large enterprises
Small/mediumenterprises
Personal use
Role of information systems
Direction of IT security
Protection of military data.
Availability for critical infrastructure
Availability for IT systems in corporations
Network security for e-commerce
Security for e-government
Safe/reliable society
1950
InternetPC
Mobile/Ubiquitous
Trends of IT Security
1949
Shannon, The Communication Theory of Secrecy Systems
1975
Diffie and Hellman
1978
RSA
1977
DES
2001
AES – FIPS 197SHA-2
IBE from Pairing
2004
ID based PKC w/o Random Oracle
2003
Certificateless PKC
1996
DifferentialFault
Analysis
1985/1987
ECC
1994
OAEP
1993
Random Oracle Model
1988
Zero Knowledge Proof
Linear Cryptanalysis
1992
Differential Cryptanalysis
1990
2002
E-Voting (Votopia)
1995
SHA-1
2000
Polynomial based PKC
1998
Impossible DifferentialCryptanalysis
2006
Power of the Randomized Iterate
DSA
1991
2005
Collisions on Hash Functions
2007
Cryptography with Constant Input Locality
2008
CCA secure encryption based on computational
problems
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History of Modern Cryptography
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What is Information Security?
Confidentiality
Integrity
Availability
Processing
Storage
Transmission
Policy & Procedures
Technology
Education, Training & Awareness
Security Properties
Information States
Security Measures
NSTISSI 4011: National Training Standard for Information Systems Security Professionals, 1994
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Information Security C.I.A.
Information Security Discipline that protects the Confidentiality, Integrity & Availability of informa-
tion, during processing, storage & transmission, through Policies, Technolo-gies & Operations
Network/Communication security, Host/Computer security
C.I.A. of Information Security Confidentiality: Protecting from unauthorized disclosure Integrity: Protecting from unauthorized modification Availability: Making information accessible/available when needed
How to Achieve Information Security Policies : what should do, what should not do, etc., for information security Technologies: implementing the policies Operations: assessment & improvement on the implemented technologies
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Managing Security
Central Security
Management
ImplementAppropriate
Policy & Controls
MonitorEffectiveness of Policy &Controls
Assess Risk & Determine
Needs
Provide SecurityAwareness,Training & Education
Ris
k A
na
lys
isLegal, RegulatoryBusiness Requirements
Identify Assets & Threats
Security Advisories and Results of Audits & Monitoring(Vulnerabilities)
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Enterprise Security Management
FW, VPN, PKI, IDS, A/V, Token
Enterprise Infrastructure
Systems, Network, Applications, Databases
EnterpriseSecurity
Management
Vulnerability Management
Threat Management
Integrity
Avai
labi
lity
Confidentiality
Introduction to Information Security
Lecture 2: Classical Ciphers
2009. 6.
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1. History of cryptographic research 2. Substitution ciphers
Caesar ciphers Affine ciphers Monoalphabetic substitution cipher Homophonic substitution cipher Polyalphabetic substitution cipher Vigenere cipher Hill cipher One-time pad
3. Transposition ciphers Transposition cipher scytale cipher
4. Product ciphers
Contents
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1. History of Cryptologic Research
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1900BC : Non-standard hieroglyphics
1500BC : Mesopotamian pottery glazes
50BC : Caesar cipher
1518 : Trithemius’ cipher book
1558 : Keys invented
1583 : Vigenere’s book
1790 : Jefferson wheel
1854 : Playfair cipher
1857 : Beaufort’s cipher
1917 : Friedman’s Riverbank Labs
1917 : Vernam one-time pads
History of Cryptologic Research
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1919 : Hegelin machines
1921 : Hebern machines
1929 : Hill cipher
1973 : Feistel networks
1976 : Public key cryptography
1979 : Secret sharing
1985 : Zero knowledge
1990 : Differential cryptanalysis
1994 : Linear cryptanalysis
1997 : Triple-DES
1998 ~ 2001 : AES
History of Cryptologic Research
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History of Cryptologic Research
Period
Manual Crypto
MachineCrypto
Modern CryptoComputer Crypto
Features Examples
ancient ~ 1920
1920 ~ 1950
SubstitutionTransposition
Using complex machine
Using computerShannon’s theory
Scytale, Caesar, Vigenere, Beaufort (USA)
Enigma (Germany in 2nd WW)M-209 (USA in 2nd WW)
DES, SEED, AESRSA, ECC, KCDSA1950 ~ current
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Before modern crypto : limited usage– National security, diplomatic, war – Used by limited people– Researched by limited people
Current crypto : widely open, standardized, commerce – Internet, e-commerce – Anybody is using – Research and development by anyone
Using Cryptologic Technology
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Scytale
as bc cy dt ea fl ge
a s
bc
cy
dt
ea
fl
ge
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Enigma(German) vs. Purple (Japan)@WWII
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Lorenz SZ42 Cipher Machine
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Classical Encryption Techniques
Basic building blocks of all encryption techniquesSubstitution: replacementTransposition: relocation
Substitution ciphersCaesar cipherMonoalphabetic ciphersPlayfair cipherHill cipherPolyalphabetic ciphers: Vigenere cipherVernam cipher/One-time pad: perfect cipher
Transposition techniquesRotor machines: Enigma, Purple
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2. Substitution Cipher
Caesar ciphersAffine ciphers Hill cipherMonoalphabetic substitution cipherHomophonic substitution cipherPolyalphabetic substitution cipherVigenere cipher One-time pad
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Caesar Ciphers
a b c d e f g h i j k ... z
0 1 2 3 4 5 6 7 8 9 10 … 25
C = EK(M) = M + K mod 26K = 3
M = DK(C) = C - K mod 26K = 3
Mathematically assign numbers to each alphabet
Caesar cipher :
Julius Caesar, the Roman emperorAlso known as shift cipher
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Caesar Ciphers
a b c d e f g h i j k ... z
D E F G H I J K L M N … C
Define transformation as:
i n f o r m a t i o n
L Q I R U P D W L R Q
Encryption example
Weakness• Key space is too short – only 26 possible keys• Brute force search
Example: Break ciphertext “L ORYH LFX"
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Affine Ciphers
Generalization of Caesar cipher
Encryption
Decryption
1)26,gcd(
26mod)(
1
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K
KMKMEC K
26mod)()( 112 KKCCDM K
Example: decrypt the following ciphertext
WZDUY ZZYQB OTHTX ZDNZD KWQHI BYQBP WZDUY ZXZDSS
How? Using English character frequency analysis…
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Letter Frequency(%) Letter Frequency(%) Letter Frequency(%) e 12.7 d 4.3 p 1.9 t 9.1 l 4.0 b 1.5 a 8.2 c 2.8 v 1.0 o 7.5 u 2.8 k 0.8 i 7.0 m 2.4 j 0.2 n 6.7 w 2.3 x 0.1 s 6.3 f 2.2 q 0.1 h 6.1 g 2.0 z 0.1 r 6.0 y 2.0
(1) Pr(e)=0.12, (2) Pr(t,a,o,i,n,s,h,r) = 0.06 ~0.09(3) Pr(d,l)=0.04 (4) Pr(c,u,m,w,f,g,y,p,b)= 0.015~0.023(5) Pr(v,k,j,x,q,z) <=0.01
English Character Frequencies
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Affine Ciphers
Z occurs 8 times E,T,A,O,I ??? D occurs 5 times E,T,A,O,I ??? Y occurs 4 times E,T,A,O,I ???W,Q,B occur 3 times E,T,A,O,I ???
Z E, D T : try to solve
17,2
26mod193
26mod425
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21
21
KK
KK
KK
reject
Try possible solutions until you get meaningful plaintext
Exercise: try yourself
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Hill Cipher
eK(x) : (y1,y2,…,ym) =(x1,x2,…,xm) K where K is m x m matrix and gcd(det K, 26) =1
dK(y) = y K-1
(Ex) K = 11 8 K-1 = 7 18 3 7 23 11
x : july, (j,u)= (9,20), (l,y) = (11,24)
(9,20) K = (3,4) = (D,E), (11,24) K = (11,22) = (L,W)
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a b c d e f g h i j k l m n o p q r s t u v w x y z
E G L T B N M Q P A O W C R X H I Y Z D S F J K U V
i n f o r m a t i o n
P R N X Y C E D P X R
Monoalphabetic Substitution Ciphers
Example : 1-1 Substitution rule
Example : Encryption
Cryptanalysis: Using English character frequency analysis…
Key space : 26!
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Homophonic Substitution Ciphers
Letters which occur frequently may be mapped into more than one letter in the ciphertext to flatten the frequency distribution.
Alphabet is mapped into the numbers 0 to 99For example, E(12.7%) 17, 19, 23, 47, 64A(8.2%) 8, 20, 25, 49 R(6.0%) 1, 29, 65T(9.1%) 16, 31, 85, 87
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Polyalphabetic Substitution Ciphers
Hide the frequency distribution by making multiple substitutions.Apply d different permutations.
),(,),(),(),(,),(),()(
,,,,,,,,
222112211
22121
ddddddK
dddd
mmmmmmmE
mmmmmmm
• Vigenere cipher
• Beauford cipher
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Polyalphabetic Substitution Ciphers
Vigenère Ciphers• Multiple caesar cipher
dikcmmmcccDm
dikmcccmmmEc
kkkkk
iiddk
iiddk
dd
,,1for 26mod),,,(),,,(
,,1for 26mod),,,(),,,(
26),,,,(
2121
2121
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dickmmmcccDm
dimkcccmmmEc
kkkkk
iiddk
iiddk
dd
,,1for 26mod),,,(),,,(
,,1for 26mod),,,(),,,(
26),,,,(
2121
2121
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Beauford ciphers (used in US civil war)
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Vigenère Ciphers
평문키워드
a b c d e f g h i j k l m n o p q r s t u v w x y z
A A B C D E F G H I J K L M N O P Q R S T U V W X Y ZB B C D E F G H I J K L M N O P Q R S T U V W X Y Z AC C D E F G H I J K L M N O P Q R S T U V W X Y Z A BD D E F G H I J K L M N O P Q R S T U V W X Y Z A B CE E F G H I J K L M N O P Q R S T U V W X Y Z A B C DF F G H I J K L M N O P Q R S T U V W X Y Z A B C D EG G H I J K L M N O P Q R S T U V W X Y Z A B C D E FH H I J K L M N O P Q R S T U V W X Y Z A B C D E F GI I J K L M N O P Q R S T U V W X Y Z A B C D E F G HJ J K L M N O P Q R S T U V W X Y Z A B C D E F G H IK K L M N O P Q R S T U V W X Y Z A B C D E F G H I JL L M N O P Q R S T U V W X Y Z A B C D E F G H I J KM M N O P Q R S T U V W X Y Z A B C D E F G H I J K LN N O P Q R S T U V W X Y Z A B C D E F G H I J K L MO O P Q R S T U V W X Y Z A B C D E F G H I J K L M NP P Q R S T U V W X Y Z A B C D E F G H I J K L M N OQ Q R S T U V W X Y Z A B C D E F G H I J K L M N O PR R S T U V W X Y Z A B C D E F G H I J K L M N O P QS S T U V W X Y Z A B C D E F G H I J K L M N O P Q RT T U V W X Y Z A B C D E F G H I J K L M N O P Q R SU U V W X Y Z A B C D E F G H I J K L M N O P Q R S TV V W X Y Z A B C D E F G H I J K L M N O P Q R S T UW W X Y Z A B C D E F G H I J K L M N O P Q R S T U VX X Y Z A B C D E F G H I J K L M N O P Q R S T U V WY Y Z A B C D E F G H I J K L M N O P Q R S T U V W XZ Z A B C D E F G H I J K L M N O P Q R S T U V W X Y
Look-up table for Vigenère Ciphers
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Vigenère Ciphers
Plaintext
Keyword
Cipher-
text
M
Su
V
Er
GAXAKIPWAKXBJSUSLNRZTMKLL
CYTIRUCESYTIRUCESYTIRUCESecestonsimetsysotpyrcsiht
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Polyalphabetic Substitution Ciphers
Cryptanalysis of polyalphabetic substitution ciphers1. Determine the period 2. Determine each substitution keys
How to determine the period? 3. Kasiski method : use repetitions in the ciphertext 4. Index of coincidence by Friedman: compute the index of co-
incidence and estimate the period
Refer to http://www.rhodes.edu/mathcs/faculty/barr/Math103CUSummer04/FriedmanKasiski.pdf
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Kasiski Method
- in this example “VTW” is repeated in 9 letters apart - suggests size of d is 3 or 9
key: deceptivedeceptivedeceptiveplaintext: wearediscoveredsaveyourselfciphertext:ZICVTWQNGRZGVTWAVZHCQYGLMGJ
Example: Vigenère Ciphers
Method developed by Kasiski • Letter groups in ciphertext are repeated because repeated let-
ter groups in the plaintext line up with the keyword.• If letter groups repeated in ciphertext, then keyword length
may be a divisor of their separations.
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One-time Pad (Vernam cipher)
Ex) Binary alphabet P : o n e t i P’: 01101111 01101110 01100101 01110100 01101001 K : 01011100 01010001 11100000 01101001 01111010 C : 00110011 00111111 10000101 00011101 00010011
Perfect Cipher : p (x|y) = p(x) for all x P, y C Impossible COA
Use a random key as long as the message size and use the key only once
Unbreakable Since ciphertext bears no statistical relationship to the
plaintext Since for any plaintext & any ciphertext there exists a key
mapping one to other Have the problem of safe distribution of key
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3. Transposition Ciphers
Transposition cipherScytale cipherRotor machines
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Transposition Ciphers
Rearrange characters of plaintext to produce ciphertext Frequency distribution of the characters is not changed by encryption
Example:
1 2 3 4 5 63 5 1 6 4 2
1 2 3 4 5 63 6 1 5 2 4
i n f o r ma t i o n s e c u r i t y x y z a b
F R I MONI NAS OT UI E T R C YAYB Z X
Encryption permutation Decryption permutation
plaintext
ciphertext
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Transposition Ciphers
Cryptanalysis : Period d is guessed by trying possible periods A knowledge of the most frequent pairs and triples in a language is used
with anagramming. Use language characteristics
Frequent pairs on a relative scale to 10 TH : 10.00, HE : 9.50, IN : 7.17, ER : 6.65, RE : 5.92
Frequent triples on a relative scale to 10 THE : 10.00, AND : 2.81, TIO : 2.24, ATI : 1.67
Exercise: decrypt the following ciphertext
LDWEOHETTHSESTRUHTELOBSEDEFEIVNT
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Scytale Cipher
as bc cy dt ea fl ge
a s
bc
cy
dt
ea
fl
ge
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4. Product Ciphers
ShannonSP Network
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Shannon’s Proposal
C. Shannon, “Communication Theory for Secrecy Systems”, 1949Compose different kind of simple and insecure ciphers to create
complex and secure cryptosystems called “product cipher”Incorporate confusion and diffusionSubstitution-Permutation Network
Claude Shannon
http://www.bell-labs.com/news/2001/february/26/1.html
http://cm.bell-labs.com/cm/ms/what/shannonday/paper.html
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Confusion and Diffusion
Confusion (substitution) : The ciphertext statistics should depend on the plaintext
statistics in a manner too complicated to be exploited by the enemy cryptanalyst
Makes relationship between ciphertext and key as complex as possible
Diffusion (permutation) :Each digit of the plaintext should influence many digits of the
ciphertext, and/orEach digit of the secret key should influence many digits of the
the ciphertext. Dissipates statistical structure of plaintext over bulk of
ciphertext
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SP Network
Substitution-Permutation network Substitution (S-box) : secret key is used Permutation (P-box) : no secret key, fixed topology
Provide confusion and diffusion
S-P networks are expected to haveAvalanche property: a single input bit change should force
the complementation of approximately half of the output bits Completeness property: each output bit should be a complex
function of every input bits
Theoretical basis of modern block ciphers
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SP Network
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Kerckhoff’s Principle
Auguste Kerckhoff, 1883 A cryptosystem should be secure even if everything about the
system, except the key, is public knowledge. Eric Raymond extends this principle in support of open source
software, saying "Any security software design that doesn't as-sume the enemy possesses the source code is already untrust-worthy; therefore, never trust closed source”.
The majority of civilian cryptography makes use of publicly-known algorithms. By contrast, ciphers used to protect classi-fied government or military information are often kept secret